WO1992000798A1 - Improvements in or relating to flow control - Google Patents

Improvements in or relating to flow control Download PDF

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Publication number
WO1992000798A1
WO1992000798A1 PCT/GB1991/001092 GB9101092W WO9200798A1 WO 1992000798 A1 WO1992000798 A1 WO 1992000798A1 GB 9101092 W GB9101092 W GB 9101092W WO 9200798 A1 WO9200798 A1 WO 9200798A1
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WO
WIPO (PCT)
Prior art keywords
membrane
tube
pores
fluid
tubular
Prior art date
Application number
PCT/GB1991/001092
Other languages
French (fr)
Inventor
William Allison
Original Assignee
Lanmark Consultants Limited
Priority date (The priority date is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the date listed.)
Filing date
Publication date
Application filed by Lanmark Consultants Limited filed Critical Lanmark Consultants Limited
Publication of WO1992000798A1 publication Critical patent/WO1992000798A1/en

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Classifications

    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B01—PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
    • B01D—SEPARATION
    • B01D67/00—Processes specially adapted for manufacturing semi-permeable membranes for separation processes or apparatus
    • B01D67/0002—Organic membrane manufacture
    • B01D67/0023—Organic membrane manufacture by inducing porosity into non porous precursor membranes
    • B01D67/0032—Organic membrane manufacture by inducing porosity into non porous precursor membranes by elimination of segments of the precursor, e.g. nucleation-track membranes, lithography or laser methods
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B01—PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
    • B01D—SEPARATION
    • B01D29/00—Filters with filtering elements stationary during filtration, e.g. pressure or suction filters, not covered by groups B01D24/00 - B01D27/00; Filtering elements therefor
    • B01D29/11—Filters with filtering elements stationary during filtration, e.g. pressure or suction filters, not covered by groups B01D24/00 - B01D27/00; Filtering elements therefor with bag, cage, hose, tube, sleeve or like filtering elements
    • B01D29/111—Making filtering elements
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B01—PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
    • B01D—SEPARATION
    • B01D29/00—Filters with filtering elements stationary during filtration, e.g. pressure or suction filters, not covered by groups B01D24/00 - B01D27/00; Filtering elements therefor
    • B01D29/11—Filters with filtering elements stationary during filtration, e.g. pressure or suction filters, not covered by groups B01D24/00 - B01D27/00; Filtering elements therefor with bag, cage, hose, tube, sleeve or like filtering elements
    • B01D29/13—Supported filter elements
    • B01D29/15—Supported filter elements arranged for inward flow filtration
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B01—PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
    • B01D—SEPARATION
    • B01D29/00—Filters with filtering elements stationary during filtration, e.g. pressure or suction filters, not covered by groups B01D24/00 - B01D27/00; Filtering elements therefor
    • B01D29/11—Filters with filtering elements stationary during filtration, e.g. pressure or suction filters, not covered by groups B01D24/00 - B01D27/00; Filtering elements therefor with bag, cage, hose, tube, sleeve or like filtering elements
    • B01D29/31—Self-supporting filtering elements
    • B01D29/35—Self-supporting filtering elements arranged for outward flow filtration
    • B01D29/356—Self-supporting filtering elements arranged for outward flow filtration open-ended, the arrival of the mixture to be filtered and the discharge of the concentrated mixture are situated on both opposite sides of the filtering element
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B01—PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
    • B01D—SEPARATION
    • B01D29/00—Filters with filtering elements stationary during filtration, e.g. pressure or suction filters, not covered by groups B01D24/00 - B01D27/00; Filtering elements therefor
    • B01D29/60—Filters with filtering elements stationary during filtration, e.g. pressure or suction filters, not covered by groups B01D24/00 - B01D27/00; Filtering elements therefor integrally combined with devices for controlling the filtration
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B01—PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
    • B01D—SEPARATION
    • B01D29/00—Filters with filtering elements stationary during filtration, e.g. pressure or suction filters, not covered by groups B01D24/00 - B01D27/00; Filtering elements therefor
    • B01D29/62—Regenerating the filter material in the filter
    • B01D29/66—Regenerating the filter material in the filter by flushing, e.g. counter-current air-bumps
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B01—PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
    • B01D—SEPARATION
    • B01D29/00—Filters with filtering elements stationary during filtration, e.g. pressure or suction filters, not covered by groups B01D24/00 - B01D27/00; Filtering elements therefor
    • B01D29/62—Regenerating the filter material in the filter
    • B01D29/70—Regenerating the filter material in the filter by forces created by movement of the filter element
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B01—PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
    • B01D—SEPARATION
    • B01D67/00—Processes specially adapted for manufacturing semi-permeable membranes for separation processes or apparatus
    • B01D67/0002—Organic membrane manufacture
    • B01D67/0023—Organic membrane manufacture by inducing porosity into non porous precursor membranes
    • B01D67/0025—Organic membrane manufacture by inducing porosity into non porous precursor membranes by mechanical treatment, e.g. pore-stretching
    • B01D67/0027—Organic membrane manufacture by inducing porosity into non porous precursor membranes by mechanical treatment, e.g. pore-stretching by stretching
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B01—PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
    • B01D—SEPARATION
    • B01D69/00—Semi-permeable membranes for separation processes or apparatus characterised by their form, structure or properties; Manufacturing processes specially adapted therefor
    • B01D69/04—Tubular membranes
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B01—PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
    • B01F—MIXING, e.g. DISSOLVING, EMULSIFYING OR DISPERSING
    • B01F23/00—Mixing according to the phases to be mixed, e.g. dispersing or emulsifying
    • B01F23/20—Mixing gases with liquids
    • B01F23/23—Mixing gases with liquids by introducing gases into liquid media, e.g. for producing aerated liquids
    • B01F23/231—Mixing gases with liquids by introducing gases into liquid media, e.g. for producing aerated liquids by bubbling
    • B01F23/23105—Arrangement or manipulation of the gas bubbling devices
    • B01F23/2312—Diffusers
    • B01F23/23124—Diffusers consisting of flexible porous or perforated material, e.g. fabric
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B01—PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
    • B01F—MIXING, e.g. DISSOLVING, EMULSIFYING OR DISPERSING
    • B01F23/00—Mixing according to the phases to be mixed, e.g. dispersing or emulsifying
    • B01F23/20—Mixing gases with liquids
    • B01F23/23—Mixing gases with liquids by introducing gases into liquid media, e.g. for producing aerated liquids
    • B01F23/231—Mixing gases with liquids by introducing gases into liquid media, e.g. for producing aerated liquids by bubbling
    • B01F23/23105—Arrangement or manipulation of the gas bubbling devices
    • B01F23/2312—Diffusers
    • B01F23/23126—Diffusers characterised by the shape of the diffuser element
    • B01F23/231265—Diffusers characterised by the shape of the diffuser element being tubes, tubular elements, cylindrical elements or set of tubes
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B23—MACHINE TOOLS; METAL-WORKING NOT OTHERWISE PROVIDED FOR
    • B23K—SOLDERING OR UNSOLDERING; WELDING; CLADDING OR PLATING BY SOLDERING OR WELDING; CUTTING BY APPLYING HEAT LOCALLY, e.g. FLAME CUTTING; WORKING BY LASER BEAM
    • B23K26/00—Working by laser beam, e.g. welding, cutting or boring
    • B23K26/36—Removing material
    • B23K26/38—Removing material by boring or cutting
    • B23K26/382—Removing material by boring or cutting by boring
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B23—MACHINE TOOLS; METAL-WORKING NOT OTHERWISE PROVIDED FOR
    • B23K—SOLDERING OR UNSOLDERING; WELDING; CLADDING OR PLATING BY SOLDERING OR WELDING; CUTTING BY APPLYING HEAT LOCALLY, e.g. FLAME CUTTING; WORKING BY LASER BEAM
    • B23K26/00—Working by laser beam, e.g. welding, cutting or boring
    • B23K26/36—Removing material
    • B23K26/38—Removing material by boring or cutting
    • B23K26/382—Removing material by boring or cutting by boring
    • B23K26/389—Removing material by boring or cutting by boring of fluid openings, e.g. nozzles, jets
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B26—HAND CUTTING TOOLS; CUTTING; SEVERING
    • B26F—PERFORATING; PUNCHING; CUTTING-OUT; STAMPING-OUT; SEVERING BY MEANS OTHER THAN CUTTING
    • B26F1/00—Perforating; Punching; Cutting-out; Stamping-out; Apparatus therefor
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B29—WORKING OF PLASTICS; WORKING OF SUBSTANCES IN A PLASTIC STATE IN GENERAL
    • B29C—SHAPING OR JOINING OF PLASTICS; SHAPING OF MATERIAL IN A PLASTIC STATE, NOT OTHERWISE PROVIDED FOR; AFTER-TREATMENT OF THE SHAPED PRODUCTS, e.g. REPAIRING
    • B29C61/00—Shaping by liberation of internal stresses; Making preforms having internal stresses; Apparatus therefor
    • B29C61/06—Making preforms having internal stresses, e.g. plastic memory
    • B29C61/0608—Making preforms having internal stresses, e.g. plastic memory characterised by the configuration or structure of the preforms
    • C—CHEMISTRY; METALLURGY
    • C02—TREATMENT OF WATER, WASTE WATER, SEWAGE, OR SLUDGE
    • C02F—TREATMENT OF WATER, WASTE WATER, SEWAGE, OR SLUDGE
    • C02F3/00—Biological treatment of water, waste water, or sewage
    • C02F3/02—Aerobic processes
    • C02F3/12—Activated sludge processes
    • C02F3/20—Activated sludge processes using diffusers
    • C02F3/201—Perforated, resilient plastic diffusers, e.g. membranes, sheets, foils, tubes, hoses
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B01—PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
    • B01D—SEPARATION
    • B01D2201/00—Details relating to filtering apparatus
    • B01D2201/04—Supports for the filtering elements
    • B01D2201/0461—Springs
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B01—PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
    • B01D—SEPARATION
    • B01D2201/00—Details relating to filtering apparatus
    • B01D2201/18—Filters characterised by the openings or pores
    • B01D2201/184—Special form, dimension of the openings, pores of the filtering elements
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B01—PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
    • B01D—SEPARATION
    • B01D2323/00—Details relating to membrane preparation
    • B01D2323/28—Pore treatments
    • B01D2323/283—Reducing the pores
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B01—PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
    • B01D—SEPARATION
    • B01D2323/00—Details relating to membrane preparation
    • B01D2323/44—Relaxation steps
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B23—MACHINE TOOLS; METAL-WORKING NOT OTHERWISE PROVIDED FOR
    • B23K—SOLDERING OR UNSOLDERING; WELDING; CLADDING OR PLATING BY SOLDERING OR WELDING; CUTTING BY APPLYING HEAT LOCALLY, e.g. FLAME CUTTING; WORKING BY LASER BEAM
    • B23K2103/00—Materials to be soldered, welded or cut
    • B23K2103/30—Organic material
    • B23K2103/42—Plastics
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B23—MACHINE TOOLS; METAL-WORKING NOT OTHERWISE PROVIDED FOR
    • B23K—SOLDERING OR UNSOLDERING; WELDING; CLADDING OR PLATING BY SOLDERING OR WELDING; CUTTING BY APPLYING HEAT LOCALLY, e.g. FLAME CUTTING; WORKING BY LASER BEAM
    • B23K2103/00—Materials to be soldered, welded or cut
    • B23K2103/50—Inorganic material, e.g. metals, not provided for in B23K2103/02 – B23K2103/26
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B29—WORKING OF PLASTICS; WORKING OF SUBSTANCES IN A PLASTIC STATE IN GENERAL
    • B29C—SHAPING OR JOINING OF PLASTICS; SHAPING OF MATERIAL IN A PLASTIC STATE, NOT OTHERWISE PROVIDED FOR; AFTER-TREATMENT OF THE SHAPED PRODUCTS, e.g. REPAIRING
    • B29C2793/00—Shaping techniques involving a cutting or machining operation
    • B29C2793/0045—Perforating
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B29—WORKING OF PLASTICS; WORKING OF SUBSTANCES IN A PLASTIC STATE IN GENERAL
    • B29L—INDEXING SCHEME ASSOCIATED WITH SUBCLASS B29C, RELATING TO PARTICULAR ARTICLES
    • B29L2031/00—Other particular articles
    • B29L2031/755—Membranes, diaphragms
    • Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
    • Y02—TECHNOLOGIES OR APPLICATIONS FOR MITIGATION OR ADAPTATION AGAINST CLIMATE CHANGE
    • Y02W—CLIMATE CHANGE MITIGATION TECHNOLOGIES RELATED TO WASTEWATER TREATMENT OR WASTE MANAGEMENT
    • Y02W10/00—Technologies for wastewater treatment
    • Y02W10/10—Biological treatment of water, waste water, or sewage

Definitions

  • This invention relates to flow control and more particularly to a membrane and a method of making a membrane in or for use in a flow control element useful in filtration or diffusion applications.
  • porous structure In many filtration and diffusion applications it is desirable to have a fine porous structure of say less than 20 ⁇ m. This is usually achieved by means of a labyrinthine pore structure using for example a ceramic material. Such porous media are particularly prone to blocking which cannot easily be cleared using conventional techniques such as back-cleaning.
  • a method of making a membrane comprising reducing the membrane after perforation to decrease the pore size.
  • the membrane is perforated in a stretched condition.
  • the method enables a membrane with relatively small pores to be made by making relatively large pores in a stretched or expanded membrane and then reducing or shrinking the membrane to decrease the pore size.
  • the membrane is made of heat shrinkable synthetic plastics material perforated in its expanded state and is reduced by heating.
  • a membrane made in accordance with the method as defined above.
  • a third aspect of the present invention provides a flow control element comprising a membrane as aforesaid wherein the membrane is preferably disposed on a support and the support may be adjustable to vary the pore size of the membrane.
  • a method of diffusing a fluid into a surrounding medium comprising placing a tubular membrane made in accordance with the method of claim 5 in said medium and introducing the fluid into the tubular membrane at a pressure such that the fluid is forced through the pores of the membrane and into the surrounding medium.
  • Fig. 1 is a side view of one embodiment of tubular membrane in accordance with the invention, prior to shrinkage;
  • Fig. 2 is a corresponding cross-section
  • Fig. 3 is an enlarged view of the encircled portion in Fig. 2;
  • Fig. 4 is a view corresponding to Fig. 3 following shrinkage
  • Fig. 5 is a diagrammatic side view partly in section of one embodiment of filter in accordance with the invention.
  • Fig. 6 is a longitudinal section of a second embodiment of filter in accordance with the invention.
  • Fig. 7 is a part sectional side view of one embodiment of filter element in accordance with the invention.
  • Fig. 8 is a sectional view of one embodiment of gas diffuser in accordance with the invention.
  • Fig. 9 is a corresponding view of a second embodiment of gas diffuser in accordance with the invention.
  • Fig. 10 is a longitudinal section of a third embodiment of gas diffuser in accordance with the invention.
  • Fig. 1 shows a membrane in the form of a tube 1 having a wall 2 penetrated throughout its length by a multiplicity of pores 3 only a narrow band of which is shown in the drawing.
  • the tube 1 is made of heat shrinkable synthetic plastics material, e.g. silicone rubber formed by extrusion followed by stretching (usually diametrically only but possibly also longitudinally) and then setting in the stretched condition, e.g. by irradiation. In this expanded state, the tube is stress-free and can be handled in the same way as any other rubber or plastics hose. On subsequently heating to a predetermined temperature the tube shrinks to its original size, typical diametral shrink ratios being from about 5 or 6 to 1 to about 1.5 to 1.
  • the pores 3 are created in the tube 1 while the latter is in its stretched condition.
  • the pores 3 are illustrated to an enlarged scale in Fig. 3. Assuming a 2:1 diametral reduction on heat shrinkage the pore frequency in the circumferential direction will double following shrinkage, as seen in Fig. 4. If the tube 1 is also shrinkable longitudinally the pore frequency in the axial direction of the tube will also increase. As best seen from a comparison of Figs. 3 and 4, the diameter of the pores 3 is reduced disproportionately to the tube diameter so as to produce much finer pores than the shrink ratio would suggest. This is because the surrounding land 4 expands into the vacant pore spaces under the compressive forces induced by the tube reduction. In fact, the resilience of the material may result in the pores being fully closed in the relaxed condition of the material.
  • the pores 3 may be produced in the heat shrinkable tube 1 by any suitable technique e.g. by mechanical perforation using needles, by laser puncturing or by spark discharge. When produced the pores 3 may be parallel sided or have a small taper from the outer diameter to the inner diameter of the wall 2 as seen in Fig. 3. A marked frustoconical shape of the pores is produced on shrinkage by differential stressing of the tube wall during reduction, the inner circumference of the tube being in relatively higher compression stress than the outer circumference. Such a pore configuration is particularly advantageous for filtration applications of the tubular membrane.
  • the tube may be pierced from the outside or the inside to create the flaps on the inside or the outside respectively.
  • the tube may also be inverted after piercing to position the flaps at the appropriate side.
  • FIG. 3 A comparison of Figs. 3 and 4 further shows that as expected the thickness of the wall 2 increases during shrinkage.
  • the wall thickness of the heat shrinkable tube 1 is selected with regard to the shrink ratio such that the wall thickness of the shrunk tube has the requisite strength characteristics.
  • the shrunk tube is both flexible and resilient.
  • Fig. 5 shows a flow control element in the form of a cross flow filter incorporating a reduced tubular membrane 5 of the kind described above.
  • the filter has a cylindrical housing 6 defining a plenum 7 closed by top and bottom caps 8, 9 respectively in which the ends of the tube 5 are fixed for communication with an inlet 10 in the top cap 8 and an outlet 11 in the bottom cap 9.
  • the housing 6 has a bottom discharge opening 12 for discharging clean filtrate from the bottom of the plenum 7. Fluid contaminated with particulate material to be filtered out is introduced through the inlet 10 and flows axially through the tube 5 and outwardly through the porous tube wall into the plenum 7 from which it is discharged through the opening 12, the particulate contaminant being retained by the pores in the tube 5.
  • the tube 5 may be semi-rigid by appropriate selection of the nature and wall thickness of the constituent plastics material.
  • the filter of Fig. 6 is of the dead-end type in which a plenum 13 defined by a cylindrical wall 14 is closed at its bottom end by an end wall 15 and at its upper end by a top cap 16 incorporating an inlet 17 for dirty fluid from a pump and an axial outlet 18 for clean filtrate discharge.
  • the inside of the top cap 16 has an axial stub 19 on which is located an annular seal 20 in sealing contact with a coaxial cylindrical filter element 21 held in the plenum 13 clear of the end wall 15 and having a sealing bottom plug 22 in its lower end.
  • the filter element 21 comprises a relatively thick walled coarsely porous inner tube of rigid or semi-rigid material 23 providing a support for an outer tubular membrane 24 having very fine pores and made by the method according to the invention.
  • the outer tube 24 may be heat shrunk onto the support 23 during manufacture.
  • fluid containing suspended material to be filtered out is passed into the plenum 13 from the inlet 17 and flows through the filter element 21 depositing solid particles in the fine pores of the outer tube 24, clean filtrate being discharged through the top opening 18.
  • Fig. 7 shows an alternative design of filter element for use in the filter of Fig. 6.
  • the membrane tube 21 made in accordance with the invention is supported (and may be heat shrunk onto) a helical spring 25 having closely adjacent coils of trapezoidal section with axial scoring 26 on the spring circumference to provide drainage runnels.
  • the spring 25 may be extended to stretch the membrane 21 and hence vary the size of the pores therein, for example to enlarge the pores for back-cleaning the filter.
  • the membrane 21 may also be expanded by introducing gas or liquid under pressure into the filter element and if the pressure is sufficient the membrane 21 may be distended so as to break off filter cake on the outside of the membrane, such filter cake preferably having been dried previously in order to facilitate removal in this way.
  • a self- supporting tubular membrane 30 projects from a body 31 defining an air plenum 32 to which air is supplied under pressure. Further tubes 30 (not shown) may be mounted in communication with the air plenum 32. Air under pressure from the plenum 32 passes into the tube 30 (which is closed at its distal end) and through the fine pores therein into the surrounding medium.
  • another fluid may be diffused in this way and the surrounding medium into which the fluid is diffused may be any medium which it is desired to treat or otherwise influence by means of the diffused fluid.
  • a diffuser may be used, for example, for the aeration of sewage or the oxygenation of a fish tank.
  • Fig. 9 shows a similar diffuser in which the same reference numerals have been used for the same components.
  • the tube 30 need not be self-supporting since it is supported by an axial rod 33 fixed at one end in the distal end cap 34 and at its opposite end in a set-screw 35 which is adjustable to vary the length of the tube 30 and hence the size of the pores therein.
  • the tube 30 is of limited axial length but in the embodiment of Fig. 10 the corresponding tubular membrane 36 may be of any desired length having a plug 37 at one end and a connection 38 at the other end to an imperforate flexible air delivery tube 39.
  • a stainless steel helical coil 40 imparting negative buoyancy to the tube 36 so that this may be laid on the bed of a river or lake.
  • the delivery tube 39 is then connected to an air compressor and fine aeration bubbles are emitted along the length of the tube 36 to aerate the tube environment.
  • negative buoyancy elements may be employed, e.g. flat, woven stainless steel mesh, chain or wire rope.
  • the heat shrunk tube of the various embodiments described has a smooth, cylindrical wall
  • the tube wall may be corrugated or convoluted, for example with axial grooves providing a ribbed configuration which tends to prevent kinking of the tube.
  • Corrugated tube is manufactured in the same way as smooth tube but using an extrusion die of appropriate configuration for the section that is to be produced. When the extruded tube is then expanded the corrugations are smoothed out to produce a smooth walled tube which can easily be perforated. On heat shrinkage the corrugations are restored along with the original tube diameter.
  • the membrane of the invention need not be tubular but may be in the form of a flat sheet or any other convenient configuration.
  • the holes or pores produced in the membrane may be as small as 0.2 ⁇ m reducing to less than 0.02 ⁇ m after heat shrinking.
  • the number of pores per unit area of shrunk membrane may be in excess of 10,000 per square inch.
  • a non-heat- shrinkable material for the membrane.
  • a tube of rubber or other elastomeric material may be stretched, perforated and then permitted to relax.
  • the tube may be stretched as it is fed to the perforating means, e.g. a needled roller. Care is taken to ensure that the elastomeric material is not stretched to such an extent that it tears on being perforated.

Abstract

A porous membrane is made by stretching a rubber or plastics material, perforating the material and then reducing the material to decrease the pore size. The material may be a heat shrinkable plastics material which has already been stretched in the course of manufacture. The material is preferably tubular in form and a support, for example a helical spring, may be disposed therein. The porous membrane may be used as a flow control element which has particular application in a method of diffusing a fluid into a surrounding medium, for example air into sewage.

Description

IMPROVEMENTS IN OR RELATING TO FLOW CONTROL
This invention relates to flow control and more particularly to a membrane and a method of making a membrane in or for use in a flow control element useful in filtration or diffusion applications.
In many filtration and diffusion applications it is desirable to have a fine porous structure of say less than 20μm. This is usually achieved by means of a labyrinthine pore structure using for example a ceramic material. Such porous media are particularly prone to blocking which cannot easily be cleared using conventional techniques such as back-cleaning.
It is an object of the present invention to provide a porous medium in which the aforesaid disadvantage is obviated or mitigated.
According to a first aspect of the present invention there is provided a method of making a membrane comprising reducing the membrane after perforation to decrease the pore size. Preferably, the membrane is perforated in a stretched condition. The method enables a membrane with relatively small pores to be made by making relatively large pores in a stretched or expanded membrane and then reducing or shrinking the membrane to decrease the pore size.
Preferably, the membrane is made of heat shrinkable synthetic plastics material perforated in its expanded state and is reduced by heating.
According to a second aspect of the present invention there is provided a membrane made in accordance with the method as defined above.
A third aspect of the present invention provides a flow control element comprising a membrane as aforesaid wherein the membrane is preferably disposed on a support and the support may be adjustable to vary the pore size of the membrane.
According to a fourth aspect of the present invention there is provided a method of diffusing a fluid into a surrounding medium, for example air into sewage comprising placing a tubular membrane made in accordance with the method of claim 5 in said medium and introducing the fluid into the tubular membrane at a pressure such that the fluid is forced through the pores of the membrane and into the surrounding medium. The invention will now be further described by way of example only, with reference to the accompanying drawings, in which:-
Fig. 1 is a side view of one embodiment of tubular membrane in accordance with the invention, prior to shrinkage;
Fig. 2 is a corresponding cross-section;
Fig. 3 is an enlarged view of the encircled portion in Fig. 2;
Fig. 4 is a view corresponding to Fig. 3 following shrinkage;
Fig. 5 is a diagrammatic side view partly in section of one embodiment of filter in accordance with the invention;
Fig. 6 is a longitudinal section of a second embodiment of filter in accordance with the invention;
Fig. 7 is a part sectional side view of one embodiment of filter element in accordance with the invention;
Fig. 8 is a sectional view of one embodiment of gas diffuser in accordance with the invention;
Fig. 9 is a corresponding view of a second embodiment of gas diffuser in accordance with the invention, and
Fig. 10 is a longitudinal section of a third embodiment of gas diffuser in accordance with the invention.
Fig. 1 shows a membrane in the form of a tube 1 having a wall 2 penetrated throughout its length by a multiplicity of pores 3 only a narrow band of which is shown in the drawing. The tube 1 is made of heat shrinkable synthetic plastics material, e.g. silicone rubber formed by extrusion followed by stretching (usually diametrically only but possibly also longitudinally) and then setting in the stretched condition, e.g. by irradiation. In this expanded state, the tube is stress-free and can be handled in the same way as any other rubber or plastics hose. On subsequently heating to a predetermined temperature the tube shrinks to its original size, typical diametral shrink ratios being from about 5 or 6 to 1 to about 1.5 to 1.
The pores 3 are created in the tube 1 while the latter is in its stretched condition. The pores 3 are illustrated to an enlarged scale in Fig. 3. Assuming a 2:1 diametral reduction on heat shrinkage the pore frequency in the circumferential direction will double following shrinkage, as seen in Fig. 4. If the tube 1 is also shrinkable longitudinally the pore frequency in the axial direction of the tube will also increase. As best seen from a comparison of Figs. 3 and 4, the diameter of the pores 3 is reduced disproportionately to the tube diameter so as to produce much finer pores than the shrink ratio would suggest. This is because the surrounding land 4 expands into the vacant pore spaces under the compressive forces induced by the tube reduction. In fact, the resilience of the material may result in the pores being fully closed in the relaxed condition of the material.
The pores 3 may be produced in the heat shrinkable tube 1 by any suitable technique e.g. by mechanical perforation using needles, by laser puncturing or by spark discharge. When produced the pores 3 may be parallel sided or have a small taper from the outer diameter to the inner diameter of the wall 2 as seen in Fig. 3. A marked frustoconical shape of the pores is produced on shrinkage by differential stressing of the tube wall during reduction, the inner circumference of the tube being in relatively higher compression stress than the outer circumference. Such a pore configuration is particularly advantageous for filtration applications of the tubular membrane. Creation of the pores by mechanical piercing may be useful in tearing an exit flap at the end of each pore so as to close it against reverse fluid flow if the pores are sufficiently large to remain open in the relaxed condition of the material. The tube may be pierced from the outside or the inside to create the flaps on the inside or the outside respectively. The tube may also be inverted after piercing to position the flaps at the appropriate side.
A comparison of Figs. 3 and 4 further shows that as expected the thickness of the wall 2 increases during shrinkage. Naturally, the wall thickness of the heat shrinkable tube 1 is selected with regard to the shrink ratio such that the wall thickness of the shrunk tube has the requisite strength characteristics. Preferably, the shrunk tube is both flexible and resilient.
Fig. 5 shows a flow control element in the form of a cross flow filter incorporating a reduced tubular membrane 5 of the kind described above. The filter has a cylindrical housing 6 defining a plenum 7 closed by top and bottom caps 8, 9 respectively in which the ends of the tube 5 are fixed for communication with an inlet 10 in the top cap 8 and an outlet 11 in the bottom cap 9. The housing 6 has a bottom discharge opening 12 for discharging clean filtrate from the bottom of the plenum 7. Fluid contaminated with particulate material to be filtered out is introduced through the inlet 10 and flows axially through the tube 5 and outwardly through the porous tube wall into the plenum 7 from which it is discharged through the opening 12, the particulate contaminant being retained by the pores in the tube 5. The tube 5 may be semi-rigid by appropriate selection of the nature and wall thickness of the constituent plastics material.
The filter of Fig. 6 is of the dead-end type in which a plenum 13 defined by a cylindrical wall 14 is closed at its bottom end by an end wall 15 and at its upper end by a top cap 16 incorporating an inlet 17 for dirty fluid from a pump and an axial outlet 18 for clean filtrate discharge. The inside of the top cap 16 has an axial stub 19 on which is located an annular seal 20 in sealing contact with a coaxial cylindrical filter element 21 held in the plenum 13 clear of the end wall 15 and having a sealing bottom plug 22 in its lower end. The filter element 21 comprises a relatively thick walled coarsely porous inner tube of rigid or semi-rigid material 23 providing a support for an outer tubular membrane 24 having very fine pores and made by the method according to the invention. The outer tube 24 may be heat shrunk onto the support 23 during manufacture. In use, fluid containing suspended material to be filtered out is passed into the plenum 13 from the inlet 17 and flows through the filter element 21 depositing solid particles in the fine pores of the outer tube 24, clean filtrate being discharged through the top opening 18.
Fig. 7 shows an alternative design of filter element for use in the filter of Fig. 6. In this case, the membrane tube 21 made in accordance with the invention is supported (and may be heat shrunk onto) a helical spring 25 having closely adjacent coils of trapezoidal section with axial scoring 26 on the spring circumference to provide drainage runnels. The spring 25 may be extended to stretch the membrane 21 and hence vary the size of the pores therein, for example to enlarge the pores for back-cleaning the filter. The membrane 21 may also be expanded by introducing gas or liquid under pressure into the filter element and if the pressure is sufficient the membrane 21 may be distended so as to break off filter cake on the outside of the membrane, such filter cake preferably having been dried previously in order to facilitate removal in this way.
The description so far has been confined to a tubular membrane for use in a flow control element in the form of a filter. Alternatively, the membrane may find application in a gas diffuser of which examples are illustrated in Figs. 8 to 10. In Fig. 8, a self- supporting tubular membrane 30 projects from a body 31 defining an air plenum 32 to which air is supplied under pressure. Further tubes 30 (not shown) may be mounted in communication with the air plenum 32. Air under pressure from the plenum 32 passes into the tube 30 (which is closed at its distal end) and through the fine pores therein into the surrounding medium. It will be appreciated that another fluid (gets or liquid) may be diffused in this way and the surrounding medium into which the fluid is diffused may be any medium which it is desired to treat or otherwise influence by means of the diffused fluid. Such a diffuser may be used, for example, for the aeration of sewage or the oxygenation of a fish tank.
Fig. 9 shows a similar diffuser in which the same reference numerals have been used for the same components. In this case, the tube 30 need not be self-supporting since it is supported by an axial rod 33 fixed at one end in the distal end cap 34 and at its opposite end in a set-screw 35 which is adjustable to vary the length of the tube 30 and hence the size of the pores therein.
In the embodiment of Figs. 8 and 9 the tube 30 is of limited axial length but in the embodiment of Fig. 10 the corresponding tubular membrane 36 may be of any desired length having a plug 37 at one end and a connection 38 at the other end to an imperforate flexible air delivery tube 39. Inside the tube 36 is a stainless steel helical coil 40 imparting negative buoyancy to the tube 36 so that this may be laid on the bed of a river or lake. The delivery tube 39 is then connected to an air compressor and fine aeration bubbles are emitted along the length of the tube 36 to aerate the tube environment.
It will be appreciated that alternative negative buoyancy elements may be employed, e.g. flat, woven stainless steel mesh, chain or wire rope.
Although the heat shrunk tube of the various embodiments described has a smooth, cylindrical wall, it will be appreciated that the tube wall may be corrugated or convoluted, for example with axial grooves providing a ribbed configuration which tends to prevent kinking of the tube. Corrugated tube is manufactured in the same way as smooth tube but using an extrusion die of appropriate configuration for the section that is to be produced. When the extruded tube is then expanded the corrugations are smoothed out to produce a smooth walled tube which can easily be perforated. On heat shrinkage the corrugations are restored along with the original tube diameter.
It will be appreciated that the membrane of the invention need not be tubular but may be in the form of a flat sheet or any other convenient configuration. The holes or pores produced in the membrane may be as small as 0.2μm reducing to less than 0.02μm after heat shrinking. The number of pores per unit area of shrunk membrane may be in excess of 10,000 per square inch.
It is within the scope of the invention to use a non-heat- shrinkable material for the membrane. For example, a tube of rubber or other elastomeric material may be stretched, perforated and then permitted to relax. The tube may be stretched as it is fed to the perforating means, e.g. a needled roller. Care is taken to ensure that the elastomeric material is not stretched to such an extent that it tears on being perforated.

Claims

1. A method of making a porous membrane, comprising reducing the membrane after perforation to decrease the pore size.
2. A method as claimed in claim 1, wherein the membrane is perforated in a stretched condition.
3. A method as claimed in claim 1 or 2, wherein the membrane is made of heat shrinkable synthetic plastics material perforated in its expanded state and the membrane is reduced by heating.
4. A method as claimed in claim 1 or 2, wherein the membrane is resiliently enlarged before perforation and subsequent relaxation.
5. A method as claimed in any one of the preceding claims, wherein the membrane is perforated by laser puncturing.
6. A method as claimed in any one of the preceding claims, wherein the membrane is tubular.
7. A membrane when made by the method of any one of the preceding claims.
8. A flow control element comprising a membrane as claimed in claim 7.
9. An element as claimed in claim 8, wherein the membrane is disposed on a support.
10. An element as claimed in claim 9, wherein the support is adjustable to vary the pore size of the membrane.
11. An element as claimed in claim 10, wherein the membrane is tubular and the support is a helical spring engaging therein.
12. A method of diffusing a fluid into a surrounding medium, for example air into sewage, comprising placing a tubular membrane made in accordance with the method of claim 5 in said medium and introducing the fluid into the tubular membrane at a pressure such that the fluid is forced through the pores of the membrane and into the surrounding medium.
PCT/GB1991/001092 1990-07-13 1991-07-04 Improvements in or relating to flow control WO1992000798A1 (en)

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* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
WO1993025484A1 (en) * 1992-06-09 1993-12-23 Lanmark (Water) Limited Fluid diffuser
US5286432A (en) * 1992-03-30 1994-02-15 Robert Schmukler Fabrication of micron-range holes in protective barriers and encapsulating materials
EP0589225A1 (en) * 1992-09-23 1994-03-30 Kimberly-Clark Corporation Method for forming ultra-microapertures in thin thermoplastic film materials and products formed thereby
EP0589224A1 (en) * 1992-09-23 1994-03-30 Kimberly-Clark Corporation method for forming a net-like material from a thermoplastic film
EP0806475A2 (en) * 1996-03-28 1997-11-12 Terumo Kabushiki Kaisha Filter apparatus and method of separating micro-tissues of an organism using said filter apparatus
WO1997043219A1 (en) * 1996-05-13 1997-11-20 Johann Staudinger Method and device for introducing a gas or gas mixture into a liquid
WO1998013306A1 (en) * 1996-09-27 1998-04-02 Plastic Specialties And Technologies Investments, Inc. Aeration pipe and method of making same
WO1998042637A1 (en) * 1997-03-25 1998-10-01 Charles Ladislav Kovacs Aerated, lightweight building products
NL1001033C2 (en) * 1994-08-24 1998-12-15 Forschungszentrum Juelich Gmbh Gas tube module with selective gas permeable hose membrane and reactors provided for cell culture technology as well as fluidized layer devices for cell culture.
WO1999048653A1 (en) * 1998-03-23 1999-09-30 Deutsche Institute für Textil- und Faserforschung Stuttgart - Stiftung des öffentlichen Rechts Water vapour permeable membrane
EP1179356A2 (en) * 2000-08-07 2002-02-13 Filterwerk Mann + Hummel Gmbh Filter element with filter media on a support member
WO2002102720A1 (en) * 2001-06-15 2002-12-27 Ott Gmbh Sewage clarification device for a clarification tank
WO2009046466A1 (en) * 2007-10-10 2009-04-16 Johann Staudinger Device for introducing gas into a fluid
US7799254B2 (en) 2000-11-20 2010-09-21 AMCOR Packaging (Australia) Pty Method for the treating films
WO2011107795A2 (en) 2010-03-02 2011-09-09 Acal Energy Ltd Bubbles generation device and method
US8833216B2 (en) 2009-08-10 2014-09-16 Amcor Limited Method and an apparatus for perforating polymeric film
CN110898688A (en) * 2019-09-26 2020-03-24 上海稀点新材料科技有限公司 Inorganic flat membrane with nano porous structure and preparation method thereof

Families Citing this family (1)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
GB9109713D0 (en) * 1991-05-03 1991-06-26 Todd John J Apparatus for the gasification of liquids

Citations (7)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US2533609A (en) * 1949-03-19 1950-12-12 Bell Aircraft Corp Process for manufacturing minutely orificed articles
FR2328498A1 (en) * 1975-10-23 1977-05-20 Bauakademie Ddr Filters made of perforated elastic sheet - which is stretched to vary aperture size, esp. for removing water from concrete mixts.
JPS555861A (en) * 1978-06-29 1980-01-17 Sumitomo Electric Ind Ltd Method of manufacturing porous tube
EP0069528A2 (en) * 1981-07-04 1983-01-12 B & R ENGINEERING LIMITED Filtration method and apparatus
JPS62148246A (en) * 1985-12-23 1987-07-02 Oji Yuka Gouseishi Kk Manufacture of perforated resin film
WO1987007590A1 (en) * 1986-06-12 1987-12-17 Wilke Engelbart Process and device for large surface-area fine-bubble gasification of liquids
JPS6323936A (en) * 1986-07-17 1988-02-01 Dainippon Printing Co Ltd Production of perforated film

Patent Citations (7)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US2533609A (en) * 1949-03-19 1950-12-12 Bell Aircraft Corp Process for manufacturing minutely orificed articles
FR2328498A1 (en) * 1975-10-23 1977-05-20 Bauakademie Ddr Filters made of perforated elastic sheet - which is stretched to vary aperture size, esp. for removing water from concrete mixts.
JPS555861A (en) * 1978-06-29 1980-01-17 Sumitomo Electric Ind Ltd Method of manufacturing porous tube
EP0069528A2 (en) * 1981-07-04 1983-01-12 B & R ENGINEERING LIMITED Filtration method and apparatus
JPS62148246A (en) * 1985-12-23 1987-07-02 Oji Yuka Gouseishi Kk Manufacture of perforated resin film
WO1987007590A1 (en) * 1986-06-12 1987-12-17 Wilke Engelbart Process and device for large surface-area fine-bubble gasification of liquids
JPS6323936A (en) * 1986-07-17 1988-02-01 Dainippon Printing Co Ltd Production of perforated film

Non-Patent Citations (3)

* Cited by examiner, † Cited by third party
Title
PATENT ABSTRACTS OF JAPAN vol. 11, no. 377 (M-649)December 9, 1987 & JP-A-62 148 246 (OJI YUKA GOUSEICHI ) July 2, 1987 see the whole document & Database WPIL (DERWENT PUBL LTD, LONDON) AN=87-224187 , Week 8732 *
PATENT ABSTRACTS OF JAPAN vol. 12, no. 230 (C-508)June 29, 1988 & JP-A-63 23 936 (DAINIPPON PRINTING CO LTD ) February 1, 1988 see the whole document & Database WPIL (DERWENT PUBL LTD, LONDON) AN=88-068439 , Week 8810 *
PATENT ABSTRACTS OF JAPAN vol. 4, no. 33 (M-003)March 21, 1980 & JP-A-55 5 861 (SUMITOMO ELECTRIC IND LTD ) January 17, 1980 see the whole document & Database WPI (DERWENT PUBL LTD, LONDON) AN=80-13912C , Week 8008 *

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US5286432A (en) * 1992-03-30 1994-02-15 Robert Schmukler Fabrication of micron-range holes in protective barriers and encapsulating materials
WO1993025484A1 (en) * 1992-06-09 1993-12-23 Lanmark (Water) Limited Fluid diffuser
EP0589225A1 (en) * 1992-09-23 1994-03-30 Kimberly-Clark Corporation Method for forming ultra-microapertures in thin thermoplastic film materials and products formed thereby
EP0589224A1 (en) * 1992-09-23 1994-03-30 Kimberly-Clark Corporation method for forming a net-like material from a thermoplastic film
NL1001033C2 (en) * 1994-08-24 1998-12-15 Forschungszentrum Juelich Gmbh Gas tube module with selective gas permeable hose membrane and reactors provided for cell culture technology as well as fluidized layer devices for cell culture.
EP0806475A2 (en) * 1996-03-28 1997-11-12 Terumo Kabushiki Kaisha Filter apparatus and method of separating micro-tissues of an organism using said filter apparatus
EP0806475A3 (en) * 1996-03-28 2001-01-17 Terumo Kabushiki Kaisha Filter apparatus and method of separating micro-tissues of an organism using said filter apparatus
WO1997043219A1 (en) * 1996-05-13 1997-11-20 Johann Staudinger Method and device for introducing a gas or gas mixture into a liquid
WO1998013306A1 (en) * 1996-09-27 1998-04-02 Plastic Specialties And Technologies Investments, Inc. Aeration pipe and method of making same
WO1998042637A1 (en) * 1997-03-25 1998-10-01 Charles Ladislav Kovacs Aerated, lightweight building products
WO1999048653A1 (en) * 1998-03-23 1999-09-30 Deutsche Institute für Textil- und Faserforschung Stuttgart - Stiftung des öffentlichen Rechts Water vapour permeable membrane
US6645379B2 (en) 2000-08-07 2003-11-11 Filterwerk Mann & Hummel Gmbh Filter element with a filter medium applied to a support body
EP1179356A3 (en) * 2000-08-07 2002-03-13 Filterwerk Mann + Hummel Gmbh Filter element with filter media on a support member
EP1179356A2 (en) * 2000-08-07 2002-02-13 Filterwerk Mann + Hummel Gmbh Filter element with filter media on a support member
US7799254B2 (en) 2000-11-20 2010-09-21 AMCOR Packaging (Australia) Pty Method for the treating films
WO2002102720A1 (en) * 2001-06-15 2002-12-27 Ott Gmbh Sewage clarification device for a clarification tank
WO2009046466A1 (en) * 2007-10-10 2009-04-16 Johann Staudinger Device for introducing gas into a fluid
US8833216B2 (en) 2009-08-10 2014-09-16 Amcor Limited Method and an apparatus for perforating polymeric film
CN102781561A (en) * 2010-03-02 2012-11-14 Acal能源公司 Bubbles generation device and method
WO2011107794A3 (en) * 2010-03-02 2012-01-12 Acal Energy Ltd Fuel cells
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WO2011107795A2 (en) 2010-03-02 2011-09-09 Acal Energy Ltd Bubbles generation device and method
KR101523187B1 (en) * 2010-03-02 2015-05-27 애칼 에너지 리미티드 Bubbles generation device and method
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CN110898689B (en) * 2019-09-26 2021-11-16 上海稀点新材料科技有限公司 Flat membrane with nano porous structure and preparation method thereof

Also Published As

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PT98308A (en) 1993-09-30
ZA915325B (en) 1992-04-29
JPH05508343A (en) 1993-11-25
IL98751A0 (en) 1992-07-15
GB9015448D0 (en) 1990-08-29
AU8198591A (en) 1992-02-04

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