Hollow fiber membrane module and method for operating same

Patent metadata

Field	Value
Publication number	US-11141698-B2
Application number	US-201616066564-A
Country	US
Kind code	B2
Filing date	Dec 26, 2016
Priority date	Dec 28, 2015
Publication date	Oct 12, 2021
Grant date	Oct 12, 2021

Abstract

The present invention provides a hollow fiber membrane module that can effectively resolve the accumulation of suspended solids within the membrane module, lower running costs, and also operate stably. The present invention relates to a hollow fiber membrane molecule provided with: a cylindrical case having a first end and a second end in the direction of height; a plurality of hollow fiber membranes accommodated within the cylindrical case; and a first potting part accommodated within the cylindrical case and attaching the plurality of hollow fiber membranes together such that the end parts of the plurality of hollow membrane fibers at a first end side of the cylindrical case are open. The hollow fiber membranes are porous hollow fiber membranes having a breaking strength of 23 MPa, and the hollow membrane module has a membrane area per unit volume of 800-3700 m2/m3. The filling fraction for the hollow fiber membranes in a cross-section orthogonal to the direction of height of the cylindrical case is 25-38%.

First claim

The invention claimed is:

1. A hollow-fiber membrane module comprising:
a cylindrical case having a first end and a second end in a height direction,
a plurality of hollow-fiber membranes housed in the cylindrical case, and
a first potting part which bonds end parts of the plurality of hollow-fiber membranes located at the first end of the cylindrical case, while the end parts of the plurality of hollow-fiber membranes are open, wherein
the hollow-fiber membrane is a porous hollow-fiber membrane and has a breaking strength of 23 MPa or more,
a membrane area per unit volume of the hollow-fiber membrane module is from 800 to 3,700 m 2 /m 3 ,
in a cross-section which perpendicularly intersects the height direction of the cylindrical case, a filling ratio of the hollow-fiber membranes is from 25% to 38%,
the hollow-fiber membrane contains a solid matter containing a fluororesin-based polymer,
at least a part of the solid matter constitutes a columnar texture,
the columnar texture is oriented in a longitudinal direction of the hollow-fiber membrane,
the columnar texture has a short-side length of from 0.5 μm to 3 μm, and
an aspect ratio of the columnar texture is 3 or more.

2. The hollow-fiber membrane module according to claim 1 , wherein
a molecular chain in the columnar texture is oriented in the longitudinal direction of the porous hollow-fiber membrane, and
in the hollow-fiber membrane, an orientation degree π of the molecular chain of the fluororesin-based polymer in the longitudinal direction of the porous hollow-fiber membrane, calculated based on the following formula (1), is 0.4 or more and less than 1.0:
Orientation degree π=(180°− H )/180°  (1)

wherein H is a half-width (°) of a diffraction intensity distribution in a circumferential direction of a wide-angle X-ray diffraction image.

3. The hollow-fiber membrane module according to claim 1 , wherein
the fluororesin-based polymer is polyvinylidene fluoride, and
an average value ν of Raman orientation parameters of the molecular chain of the polyvinylidene fluoride, calculated based on the following formula (2), is 3.0 or more:
Raman orientation parameter=( I 1270/ I 840)parallel/( I 1270/ I 840)perpendicular  (2)

wherein:
parallel condition: the longitudinal direction of the porous hollow-fiber membrane is parallel to a polarization direction; perpendicular condition: the longitudinal direction of the porous hollow-fiber membrane is orthogonal to the polarization direction; I1270 parallel: the intensity of Raman band at 1,270 cm −1 under parallel condition; I1270 perpendicular: the intensity of Raman band at 1,270 cm −1 under perpendicular condition; I840 parallel: the intensity of Raman band at 840 cm −1 under parallel condition; and I840 perpendicular: the intensity of Raman band at 840 cm −1 under perpendicular condition.

4. The hollow-fiber membrane module according to claim 1 , wherein
the molecular chain in the columnar texture is oriented in the longitudinal direction of the porous hollow-fiber membrane,
the average value ν of Raman orientation parameters of the molecular chain, calculated based on the following formula (2), is from 1.5 to 4.0, and
in the hollow-fiber membrane, the orientation degree π of the molecular chain of the fluororesin-based polymer in the longitudinal direction of the porous hollow-fiber membrane, calculated based on the following formula (1), is less than 0.4, or
the molecular chain of the fluororesin-based polymer is non-oriented:
Raman orientation parameter=( I 1270/ I 840)parallel/( I 1270/ I 840)perpendicular  (2)

wherein
parallel condition: the longitudinal direction of the porous hollow-fiber membrane is parallel to the polarization direction; perpendicular condition: the longitudinal direction of the porous hollow-fiber membrane is orthogonal to the polarization direction; I1270 parallel: the intensity of Raman band at 1,270 cm −1 under parallel condition; I1270 perpendicular: the intensity of Raman band at 1,270 cm −1 under perpendicular condition; I840 parallel: the intensity of Raman band at 840 cm −1 under parallel condition; and I840 perpendicular: the intensity of Raman band at 840 cm −1 under perpendicular condition) condition, and
Orientation degree π=(180°− H )/180°  (1)

wherein H is a half-width (°) of a diffraction intensity distribution in the circumferential direction of a wide-angle X-ray diffraction image.

5. The hollow-fiber membrane module according to claim 1 , wherein a thickness uniformity of the columnar texture is 0.50 or more.

6. The hollow-fiber membrane module according to claim 2 , wherein
the half-width H in formula (1) is a half-width of an intensity distribution obtained by circumferentially scanning a crystal peak (2θ=20.4°) derived from a (110) plane of polyvinylidene fluoride in the wide-angle X-ray diffraction measurement.

7. A method for operating the hollow-fiber membrane module according to claim 1 , comprising:
(1) a membrane separation step of feeding raw water containing suspended substances to the hollow-fiber membrane module to separate suspended substances from a liquid, and
(2) a cleaning step of cleaning suspended substances accumulated on a membrane surface of the hollow-fiber membrane or between membrane bundles while stopping the step (1), wherein
in the cleaning step (2),
(A) a backwashing step of passing water from a permeation side of the hollow-fiber membrane to a raw water side of the hollow-fiber membrane, and
(B) a washing step of flowing the raw water or water having at least a lower suspended substance concentration than in the raw water to the raw water side of the hollow-fiber membrane at a flow rate corresponding to a membrane surface linear velocity of from 0.3 to 5.0 m/s,
are combined.

8. The method for operating a hollow-fiber membrane module according to claim 7 , wherein
an operation cycle including one step for each of the step (1) and the step (2) is repeated,
in an operation cycle group composed by repeating the operation cycle, the membrane surface linear velocity of the washing step (B) is variably set for each operation cycle, and
the membrane surface linear velocity of 1 to 50% of the washing step (B) relative to the total number of washing steps (B) included in the operation cycle group is 1.0 m/s or more.

9. The method for operating a hollow-fiber membrane module according to claim 8 , wherein
in the operation cycle group, the step (1) in at least some operation cycles are operated while conducting a cross-flow on the raw water side of the hollow-fiber membrane at a flow rate corresponding to a membrane surface linear velocity of from 0.3 to 5.0 m/s.

10. The method for operating a hollow-fiber membrane module according to claim 8 , wherein
in the operation cycle group, the step (2) in at least some operation cycles do not include the washing step (B).

11. The method for operating a hollow-fiber membrane module according to claim 9 , wherein
in the operation cycle group, the step (2) in at least some operation cycles do not include the washing step (B).

12. The hollow-fiber membrane module according to claim 1 , wherein an outside diameter of the hollow-fiber membrane is from 0.5 to 1.2 mm.

Assignees

• Toray Industries

Inventors

• SHIMURA Shun
• Iwai Kenta
• Hanakawa Masayuki
• Kitade Tamotsu
• Kimura Masahiro
• Kobayashi Atsushi
• NISHIO Aya

Classifications

• B01D63/0224 Primary

  Opening the fibre ends after encapsulation · CPC title

• B01D2321/10

  Use of feed · CPC title

• C02F1/444

  by ultrafiltration or microfiltration · CPC title

• B01D69/08

  Hollow fibre membranes (manufacture of hollow fibres D01D5/24, D01F1/08) · CPC title

• B01D2321/12

  Use of permeate · CPC title