Method for purifying aqueous suspension

• US 6,495,041 B2
• Filed: 09/14/2001
• Issued: 12/17/2002
• Est. Priority Date: 04/20/1999
• Status: Expired due to Term

• Current Assignee: Asahi Kasei Kogyo Kabushiki Kaisha (Asahi Kasei Corporation)
• Original Assignee: Asahi Kasei Kogyo Kabushiki Kaisha (Asahi Kasei Corporation)
• Inventors: Otoyo, Takehiko, Taniguchi, Tohru, Suga, Nobuhiko
• Primary Examiner(s): Drodge, Joseph W.
• Application Number:
  US09/951,631
• Publication Number:
  US 20020056682A1
• Time in Patent Office: 459 Days
• Field of Search: 202/32, 203/218.8, 203/218.9, 205/002.3, 264/41, 264/45.1, 264/49, 264/299, 264/319, 264/340, 264/348, 264/45.9, 264/46.1, 96/8, 96/10
• US Class Current: 210/321.89
• CPC Class Codes: B01D 2321/04 Backflushing
• CPC Class Codes: B01D 2321/162 Use of acids
• CPC Class Codes: B01D 2321/168 Use of other chemical agents
• CPC Class Codes: B01D 2321/185 Aeration
• CPC Class Codes: B01D 2321/2066 Pulsated flow
• CPC Class Codes: B01D 61/14 Ultrafiltration; Microfiltration
• CPC Class Codes: B01D 61/145 Ultrafiltration
• CPC Class Codes: B01D 61/147 Microfiltration
• CPC Class Codes: B01D 61/20 Accessories; Auxiliary operations
• CPC Class Codes: B01D 63/02 Hollow fibre modules
• CPC Class Codes: B01D 63/0233 forming the bundle
• CPC Class Codes: B01D 63/025 Bobbin units
• CPC Class Codes: B01D 63/06 Tubular membrane modules
• CPC Class Codes: B01D 65/02 Membrane cleaning or sterilisation ; Membrane regeneration
• CPC Class Codes: B01D 65/08 Prevention of membrane fouling or of concentration polarisation
• CPC Class Codes: B01D 69/00 Semi-permeable membranes for separation processes or apparatus characterised by their form, structure or properties; Manufacturing processes specially adapted therefor
• CPC Class Codes: B01D 69/08 Hollow fibre membranes manufacture of hollow fibres D01D5/24, D01F1/08
• CPC Class Codes: B01D 69/084 Undulated fibres
• CPC Class Codes: C02F 1/441 by reverse osmosis
• CPC Class Codes: C02F 1/444 by ultrafiltration or microfiltration
• CPC Class Codes: C02F 1/78 : with ozone C02F1/4672 takes precedence
• CPC Class Codes: C02F 2303/16 : Regeneration of sorbents, filters

Abstract

A method and apparatus for purifying an aqueous suspension comprising feeding an aqueous suspension containing fine particles comprising an inorganic component from the outer surface of a wavy hollow fiber membrane having an outer diameter of from 0.5 to 3.1 mm to filter, followed by physical wash of the hollow fiber membrane. The purifying method can reduce the damage of the membrane outer surface during the physical wash step, prevent open pores on the surface from covering and achieve stable filtration. The hollow fiber membrane bundle can be produced by having a pulsation flow contacted with the hollow fiber material being extruded from the double spinning nozzle under specific conditions and cooling and solidifying or coagulating it while shaking.

Claims

1. A hollow fiber membrane bundle which is prepared by collecting a plurality of wavy hollow fiber membranes so as to orient in a same direction with a bulkiness of from 1.45 to 2.00, the bulkiness being defined by S1/S2, where S1 is a cross sectional area of bundle of a given number of hollow fiber membranes and S2 is a cross sectional area of a single hollow fiber membrane multiplied by the given number of hollow fiber membranes,

wherein the membrane has an inner diameter of from 0.3 to 1.7 mm, an outer diameter of from 0.5 to 3.1 mm, a membrane thickness of from 0.1 to 0.7 mm, and a flatness of from 0.8 to 1.0, where the flatness is a ratio of an inner minor axis to an inner major axis of the hollow fiber membrane.

2. The hollow fiber membrane bundle according to claim 1, wherein the flatness is from 0.9 to 1.0.

3. The hollow fiber membrane bundle according to claim 1, wherein the flatness is from 0.95 to 1.0.

4. The hollow fiber membrane bundle according to claim 1, wherein the membrane includes at least one material selected from the group consisting of polyethylene, polypropylene, polybutene, tetrafluoroethylene-perfluoroalkyl vinyl ether copolymer (PFA), tetrafluoroethylene-hexafluoropropylene copolymer (FEP), tetrafluoroethylene-hexafluoropropylene-perfluoroalkylvinylether copolymer (EPE), ethylene-tetrafluoroethylene copolymer (ETFE), polychlorotrifluoroethylene (PCTFE), chlorotrifluoroethylene-ethylene copolymer (ECTFE), polyvinylidene fluoride (PVDF), polysulfone, polyether sulfone, polyether ketone, polyether ether ketone, polyphenylene sulfide, cellulose acetate, ethyl cellulose, polyacrylonitrile, and polyvinyl alcohol.

5. The hollow fiber membrane bundle according to claim 1, wherein the membrane has an average pore diameter of 0.001 to 1 μ

m.

6. The hollow fiber membrane bundle according to claim 1, wherein the membrane has an average pore diameter of 0.05 to 1 μ

m.

7. The hollow fiber membrane bundle according to claim 1, wherein the membrane has a porosity of 50 to 90%.

8. A method for producing a hollow fiber membrane bundle comprising the steps of:

i) extruding membrane production raw liquid in the form of a hollow fiber through a co-axial tube-in-orifice spinning nozzle to obtain a hollow fiber material,

ii) cooling and solidifying or coagulating the hollow fiber material to obtain a hollow fiber membrane, and

iii) collecting a plurality of the hollow fiber membranes so as to orient in the same direction;

wherein the hollow fiber material is contacted by pulsation flow before or during the cooling and solidifying or coagulating step.

9. The method according to claim 8, wherein the membranes have a bulkiness of from 1.45 to 2.00, the bulkiness being defined by S1/S2, where S1 is a cross sectional area of bundle of a given number of hollow fiber membranes and S2 is a cross sectional area of a single hollow fiber membrane multiplied by the given number of hollow fiber membranes, and the membrane has an inner diameter of from 0.3 to 1.7 mm, an outer diameter of from 0.5 to 3.1 mm, a membrane thickness of from 0.1 to 0.7 mm, and a flatness of from 0.8 to 1.0, where the flatness is a ratio of an inner minor axis to an inner major axis of the hollow fiber membrane.

10. The method according to claim 8, wherein the membrane includes at least one material selected from the group consisting of polyethylene, polypropylene, polybutene, tetrafluoroethylene-perfluoroalkyl vinyl ether copolymer (PFA), tetrafluoroethylene-hexafluoropropylene copolymer (FEP), tetrafluoroethylene-hexafluoropropylene-perfluoroalkylvinylether copolymer (EPE), ethylene-tetrafluoroethylene copolymer (ETFE), polychlorotrifluoroethylene (PCTFE), chlorotrifluoroethylene-ethylene copolymer (ECTFE), polyvinylidene fluoride (PVDF), polysulfone, polyether sulfone, polyether ketone, polyether ether ketone, polyphenylene sulfide, cellulose acetate, ethyl cellulose, polyacrylonitrile, and polyvinyl alcohol.

11. The method according to claim 8, wherein the membrane has an average pore diameter of 0.001 to 1 μ

m.

12. The method according to claim 8, wherein the membrane has an average pore diameter of 0.05 to 1 μ

m.

13. A hollow fiber membrane module, wherein a plurality of wavy hollow fiber membranes each having an inner diameter of 0.3 to 1.7 mm, an outer diameter of 0.5 to 3.1 mm, a membrane thickness of 0.1 to 0.7 mm and a flatness of 0.8 to 1.0, where the flatness is a ratio of an inner minor axis to an inner major axis of the hollow fiber membrane, is collected so as to orient in a same direction with a bulkiness of from 1.45 to 2.00, the bulkiness being defined by S1/S2, where S1 is a cross sectional area of a bundle of a given number of hollow fiber membranes and S2 is a cross sectional area of a single hollow fiber membrane multiplied by the given number of hollow fiber membranes, and mounted with a packing ratio of from 35 to 55%.

14. The hollow fiber membrane module according to claim 13, wherein the membrane includes at least one material selected from the group consisting of polyethylene, polypropylene, polybutene, tetrafluoroethylene-perfluoroalkyl vinyl ether copolymer (PFA), tetrafluoroethylene-hexafluoropropylene copolymer (FEP), tetrafluoroethylene-hexafluoropropylene-perfluoroalkylvinylether copolymer (EPE), ethylene-tetrafluoroethylene copolymer (ETFE), polychlorotrifluoroethylene (PCTFE), chlorotrifluoroethylene-ethylene copolymer (ECTFE), polyvinylidene fluoride (PVDF), polysulfone, polyether sulfone, polyether ketone, polyether ether ketone, polyphenylene sulfide, cellulose acetate, ethyl cellulose, polyacrylonitrile, and polyvinyl alcohol.

15. The hollow fiber membrane module according to claim 13, wherein the membrane has an average pore diameter of 0.001 to 1 μ

m.

16. The hollow fiber membrane module according to claim 13, wherein the membrane has an average pore diameter of 0.05 to 1 μ

m.

17. The hollow fiber membrane module according to claim 13, wherein the membrane has a porosity of 50 to 90%.