WO2011150210A2

WO2011150210A2 - Hollow fiber membrane module

Info

Publication number: WO2011150210A2
Application number: PCT/US2011/038139
Authority: WO
Inventors: Manabu Sasakawa
Original assignee: Hydranautics Corp; Mitsubishi Rayon America Inc
Current assignee: Hydranautics Corp; Mitsubishi Rayon America Inc
Priority date: 2010-05-27
Filing date: 2011-05-26
Publication date: 2011-12-01
Anticipated expiration: 2012-11-27
Also published as: WO2011150210A3

Abstract

The present invention provides a hollow fiber membrane module that can minimize the decrease of the membrane filling rate caused by arrangement of diffuser pipes, and sufficiently carry out air bubbling. The hollow fiber membrane module includes a hollow fiber membrane bundle made up with a plurality of hollow fiber membranes, an upper potting section and a lower potting section in which ends of the hollow fiber membrane bundle are put together by the use of a resin in such a way that the hollow fiber membranes maintain opening at ends, and a diffuser pipe arranged on an upper surface of the lower potting section. A cross-sectional shape of the diffuser pipe is a longer shape in a vertical direction than in a horizontal direction. A cross-sectional area of the diffuser pipe continuously and step-by-step becomes narrow toward a terminal end from an air inlet side that supplies air to the diffuser pipe.

Description

HOLLOW FIBER MEMBRANE MODULE

The present invention claims the benefit of U.S. Provisional Patent Application No. 61/348, 922 filed on May 27, 2010, which is hereby incorporated by reference.

BACKGROUND OF THE INVENTION FIELD OF THE INVENTION

The present invention relates to a hollow fiber membrane module.

DISCUSSION OF THE RELATED ART

Lately, in treating city water and sewage or industrial feed water, the hollow fiber membrane filtering technique in which hollow fiber membranes are immersed in the feed water to separate and remove impurities therefrom has been used popularly.

However, in the hollow fiber membrane filtering technique, hours of operation form an deposit layer of suspension materials, organic materials, and the like in feed water on the outer surface of the hollow fiber membrane, thereby causing clogging or fouling due to solids.

Fouling increases pressure between membranes and reduces flux during filtering, thus adversely affects the overall operating efficiency of the water treatment system.

The deterioration of operating efficiency of the water treatment system due to fouling can be overcome by physically cleaning hollow fiber membranes. For instance, the degree of fouling can be controlled to remain within a given range in such a way that, after a filtering process is performed for a given period of time, physical cleaning is undertaken, and the filtering process and physical cleaning are repeated. Physical cleaning techniques that remove deposited materials by physical interactions include: reverse cleaning in which membrane-filtered water is returned backward; running water- washing in which foulants are washed with running water on the primary side-surface, namely the feed- water-contacting surface; and air bubbling in which hollow fiber membranes are vibrated through air; and so on. Among these physical cleaning techniques, air bubbling is an effective means to mitigate fouling and is essential for stabilizing filtering operation.

Usually, air bubbling is carried out by feeding air from diffuser pipes that are arranged near the lower part of hollow fiber membranes. For instance, for hollow fiber membrane modules having diffuser pipes, the following types are known.

In a hollow fiber membrane module in which multiple hollow fiber membranes are put together at vertical angles to form a hollow fiber membrane bundle in which respective upper section and lower section are bundled by a potting section, said hollow fiber membrane module further comprises a single diffuser pipe arranged above the lower potting section (FIG. 4 of Patent Application Publication (Kokai) No. H6-343837).

However, in the hollow fiber membrane module, the hollow fiber membrane cannot be arranged in a place where the diffuser pipes are arranged, thereby causing a problem in that the membrane filling ratio in the hollow fiber membrane module is decreased. This problem becomes obvious when the number of the diffuser pipes is increased. If the diameters of the diffuser pipes are reduced, and the projected areas, viewed from the upside of a vertical direction, of the diffuser pipes are reduced, an area for arranging the hollow fiber membrane can be increased. However, due to the increase of the air velocity inside the diffuser pipes and the increase of the pressure loss, the air bubbling cannot be carried out sufficiently. Moreover, when the pressure loss increases, the consumption of transportation energy also increases.

SUMMARY OF THE INVENTION

The present invention provides a hollow fiber membrane module which can minimizes the decrease of the membrane filling ratio, which is caused by arranging the diffuser pipes, so as to sufficiently perform the air bubbling.

The hollow fiber membrane module of the present invention is characterized by the fact that it includes a hollow fiber membrane bundle made up with multiple hollow fiber membranes; a potting section in which respective upper and lower ends of said hollow fiber membrane bundle are put together by the use of a resin in such a way that the hollow fiber membranes maintain opening at ends; and a diffuser pipe arranged on or in the proximity of the upper surface of the lower potting section, wherein the diffuser pipe has a cross-sectional shape that is longer in a vertical direction than in a horizontal direction.

The hollow fiber membrane module of the present invention is characterized by the fact that it includes a hollow fiber membrane bundle made up with multiple hollow fiber membranes; a potting section in which respective upper and lower ends of said hollow fiber membrane bundle are put together by the use of a resin in such a way that the hollow fiber membranes maintain opening at ends; and a diffuser pipe arranged on or in the proximity of the upper surface of the lower potting section, wherein the diffuser pipe has a cross-sectional area that becomes, continuously and step-by-step, narrow toward a terminal end side from an air inlet side at which air is supplied to the diffuser pipe.

The hollow fiber membrane module of the present invention may further include a case in which the hollow fiber membrane bundle is housed and is fixed via the potting section.

It is preferable that the diffuser pipe is extended radially in more than three directions.

It is preferable that part of the diffuser pipe be buried in the lower potting section.

The diffuser pipe may also be used as a feeding and exhausting pipe from which water to be treated is fed and/or discharged. The present invention provides a hollow fiber membrane module that can minimizes the decrease of the membrane filling ratio, which is caused by arranging the diffuser pipes, so as to sufficiently perform the air bubbling.

BRIEF DESCRIPTION OF THE DRAWINGS

[FIG. 1] This is a cross section view showing an exemplary embodiment of the hollow fiber membrane module of the present invention.

[FIG. 2] This is a top view showing an example of the diffuser pipe thereof.

[FIG. 3] This is a cross section view along III-III of FIG. 2.

[FIG. 4] This is a cross section view showing another exemplary embodiment of the hollow fiber membrane module of the present invention.

[FIG. 5] This is a cross section view showing another example of the diffuser pipe thereof.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

<First Embodiment

FIG. 1 is a cross section view showing an exemplary embodiment of a hollow fiber membrane module of the present invention. A hollow fiber membrane module 10 is a vertical type casing module that comprises a hollow fiber membrane bundle 14 in which multiple hollow fiber membranes 12 are arranged in the vertical direction; an upper potting section 16, in which the upper end of hollow fiber membrane bundle 14 adheres to and put together in a fluid tight manner by a resin such that hollow fiber membranes 12 maintain opening at the end; a lower potting section 18, in which the lower end of hollow fiber membrane bundle 14 adheres to and put together in a fluid tight manner by a resin in such a way that the hollow fiber membranes 12 maintain opening at the end; a cylindrical case 20 in which hollow fiber membrane bundle 14 is housed and adhesively fixed to the upper and lower sections in a liquid tight manner via the upper potting section 16 and the lower potting section 18; a semicircular upper drainage section 24 that includes: an inner section, which is connected to the upper end of the case 20 so as to communicate with the inner section of hollow fiber membrane 12, and a side section, which is provided with upper treated water discharge pipe 22; a semicircular lower drainage section 28 that includes an inner section, which is connected to the lower end of the case 20 so as to communicate with the inner section of the hollow fiber membrane 12, and a side section, which is provided with the lower treated water discharge pipe 26; a feed-water/gas discharge pipe 34 that passes through the center section of upper drainage section 24 and the upper potting section 16 in the vertical angle direction, and includes a lower end that is sealed by a seal section 30, and the area, which protrudes downward from the upper potting section 16 and is provided with four feed-water/gas inlets 32; a feed-water/gas discharge pipe 38 that passes through the center section of the lower drainage section 28 and the lower potting section 18 in the vertical angle direction, and includes a lower end that is sealed by a seal section 36; four diffuser pipes 40 that extend radially in four directions from four positions of the feed-water/gas discharge pipe 38 that is arranged in such a way that part of lower half is buried in the upper surface of the lower potting section 18, and protrudes upward from the lower potting section 18; and a support pipe 50 in which, although an upper end is connected to the lower end of feed-water/gas discharge pipe 34, and the lower end is connected to the upper end of feed-water/gas discharge pipe 38; communication is interrupted by each sealed section.

The hollow fiber membrane module 10 performs a feed water filtration process as described below.

During the filtration process, by opening a first valve and a second valve (not illustrated) that are connected to the upper treated water discharge pipe 22 and the lower treated water discharge pipe 26 respectively, a passage is established from the interior of the upper drainage section 24 and that of lower drainage section 28 to a treatment tank (not illustrated). Moreover, by closing a third valve (not illustrated) connected to the feed-water/gas discharge pipe 34, the interior of case 20 is sealed internally.

Feed water fed from the feed-water/gas feed and discharge pipe 38 through a first pump (not illustrated) is discharged from aeration holes 44 into the case 20 through the diffuser pipes 40.

As the feed water permeates from a primary side (outside) to a secondary side (inside) of the hollow fiber membrane 12 in the case 20, it is filtered to separate and remove impurities. The treated water permeated into the secondary side (inside) of the hollow fiber membrane 12 comes out from an opening at the end of the hollow fiber membrane 12 to the upper drainage section 24 and to the lower drainage section 28 to be discharged from the upper treated water discharge pipe 22 and the lower treated water discharge pipe 26 to a tank.

By opening the third valve (not illustrated) that is connected to the feed-water/gas discharge pipe 34, the feed water that did not permeate through the hollow fiber membrane 12 in the case 20 goes into the feed-water/gas discharge pipe 34 from the feed-water/gas inlet 32, and is discharged from the feed-water/gas discharge pipe 34.

After the completion of the filtration process, by stopping operating each pump, the feed water in the case 20 is discharged from the feed-water/gas feed and discharge pipe 38 through the diffuser pipes 40. Moreover, after the completion of the filtration process, in order to clean the hollow fiber membranes physically by air bubbling, gases alone or gases and liquid (feed water, etc.) are fed simultaneously from the feed-water/gas feed and discharge pipe 38 while the feed water is still left in the case 20, and are discharged into the case 20 from the aeration holes 44 of the diffuser pipes 40. The hollow fiber membranes 12 are vibrated by blowing gases from the aeration holes 44 to remove materials deposited on the surfaces of the hollow fiber membranes 12 through physical interactions.

(Hollow Fiber Membrane Bundle)

The hollow fiber membranes 12 are simply put together to make the hollow fiber membrane bundle 14.

The hollow fiber membranes can be roughly classified by a pore size into the following types: reverse osmosis membrane; ultrafiltration membrane; microfiltration membrane; and large pore membrane, and the like. Any type can be used for the hollow fiber membrane 12. However, ultrafiltration membrane, microfiltration membrane, and large pore membrane having a pore size in the range of 0.005 ~ 5.0 μιη are preferable.

For the hollow fiber membrane 12, materials such as polysulfone, polyethersulfon, polyacrylonitrile, polyimide, polyetherimide, polyamide, polyetherketone, polyetheretherketone, polyethylene, polypropylene, poly-4-methypentene, cellulose, cellulose acetate, vinylidene polyfluoride, polyethylene-tetrafluoroethylene copolymer, polytetraf uoroethylene, and the like may be used. Alternatively, these materials may be combined to make composite membranes. (Potting Section)

For each potting section, resins such as epoxy resin, urethane resin, unsaturated polyester resin, silicone resin, various types of thermoplastic resin, and the like may be used. (Case, Drainage Section, and Pipe)

For the case 20, drainage section, and pipes, materials such as polycarbonate, polysulfone, polyolefme, modified-polyphenyleneether, ABS resin, polyvinyl chloride, stainless steel, and the like may be used. Fiber reinforced resins in the form of glass fibers or carbon fibers may also be used.

(Diffuser Pipe)

As illustrated in FIG. 2, the diffuser pipes 40 are oval-cross-sectional pipes extending toward the circumference from four positions on the circular wall of the feed-water/gas feed and discharge pipe 38 that protrudes upward from the center of the lower potting section 18.

The interior of the diffuser pipe 40 communicates with the interior of the feed-water/gas feed and discharge pipe 38 at the base end that provides the feeding port of the diffuser pipe 40, and is sealed by sealing cap 42 at the terminal end.

The diffuser pipe 40 has a side wall on which an array of five aeration holes 44 is arranged longitudinally. The aeration holes 44 formed on the upper half of the diffuser pipe 40 are open in such a way that the lines that are orthogonal to the center axis of the diffuser pipe 40 and pass center lines of the holes are in the vertical direction.

The diffuser pipe 40 of the first embodiment has a vertical cross-sectional shape in a length direction, which is a longer shape in the vertical direction than in the horizontal direction. In other words, the diffuser pipe 40 is shaped as being flat in the horizontal direction. When the cross-section shape of the diffuser pipe 40 is flat in the horizontal direction, the velocity of air or fluid flowing inside the pipe can be reduced, thereby decreasing the pressure loss, and also the projected area of the diffuser pipe 40 becomes smaller if viewed from the upside of the vertical direction. It is preferable that the ratio of a long diameter "a" to a short diameter "b" (a/b) for the cross-sectional shape of the diffuser pipe 40 is 1.2 to 10.

It is preferable that the diffuser pipe 40 has a cross-sectional area having an average air flow rate of less than 20 m/s.

In order to prevent an increase in resistivity, it is preferable that the aeration holes 44 have an open area having an average air flow rate of less than 20 m/s at aeration holes. It is also preferable that the total open area of the aeration holes 44 per diffuser pipe 40 be equal to the cross sectional area of the diffuser pipe 40 or less. Furthermore, if feed water contains solids, it is preferable that the aeration holes 44 have an open area of more than 3 mm² in view of fouling of the aeration holes 44.

(Effects from Operation)

In the hollow fiber membrane module 10 of the first embodiment as described above, since the cross-sectional shape of the diffuser pipe 40 is a longer shape in the vertical direction than in the horizontal direction, compared to arranging the conventional diffuser pipe that has a circle cross-sectional shape, the projected area of the diffuser pipe 40 can be reduced if viewed from the upside of the vertical direction without decreasing the cross-sectional area of the diffuser pipe 40. For this reason, without reducing the amount of air supplied to the diffuser pipe 40, the area of arranging the hollow fiber membrane 12 can be increased, thereby minimizing the decrease of the membrane filling rate caused by the arrangement of the diffuser pipe 40 and sufficiently carrying out the air bubbling.

Further, since the diffuser pipe 40 is arranged such that part of the lower half is buried in the lower potting section 18, the diffuser pipe 40 can be fully secured, and the gap under the diffuser pipe 40 is eliminated. Thus, the amount of solids accumulated under the diffuser pipe 40 can be reduced.

Moreover, since the diffuser pipe 40 also functions as a feed and discharge pipe to feed and/or discharge feed water, the hollow fiber membrane module 10 can have a simpler structure. (The Second Embodiment)

FIG. 4 is a cross section view showing a second exemplary embodiment of the hollow fiber membrane module of the present invention.

In the second exemplary embodiment, the descriptions about the same structures as those in the first exemplary embodiment are omitted.

(Diffuser Pipe)

A diffuse pipe 40 of the second exemplary embodiment, as shown in FIG. 5, is characterized in that the area of the vertical cross-section in the length direction continuously becomes narrow toward the terminal end side from the air inlet side at which air is supplied to the diffuser pipe 40. By facing the terminal end side of the diffuser pipe 40, since the air goes out from aeration holes 44 and the amount of air flowing inside the diffuser pipe 40 gradually decreases, the cross-sectional area of the diffuser pipe 40 can gradually become narrow toward the terminal end, and therefore the projected area of the diffuser pipe 40, which is viewed from the upside of the vertical direction, can be reduced.

(Effects from Operation)

In the hollow fiber membrane module 10 of the second embodiment as described above, since the cross-sectional area of the diffuser pipe 40 continuously become narrow toward the terminal end from the air inlet side in accordance with the decrease of the amount of air flowing, compared to the related art in which the diffuser pipes are arranged on the cross-sectional area from the air inlet side toward the terminal end, the projected area of the diffuser pipe viewed from the upside of the vertical direction can be reduced without decreasing the amount of air supplied to the diffuser pipe 40. For this reason, the area of arranging the hollow fiber

membrane 12 can be increased, thereby minimizing the decrease of the membrane filling rate caused by the arrangement of the diffuser pipe 40 and sufficiently performing the air bubbling.

Moreover, since the diffuser pipe 40 also functions as a feed and discharge pipe to feed and/or discharge feed water, the hollow fiber membrane module 10 can have a simpler structure. (Alternative Modes)

Note that the hollow fiber membrane module of the present invention is not limited to the hollow fiber membrane module 10 as illustrated in the drawings.

For instance, without providing the case 20, the upper potting section 16 may be fixed to the upper drainage section 24 in a liquid tight manner, and the potting section 18 may also be fixed to the lower drainage section 28 in a liquid tight manner.

The cross-sectional shape of the diffuser pipe 40 in the first embodiment may be longer in the vertical direction than in the horizontal direction. For example, the cross-sectional shape may be rectangular, polygon or the like.

The cross-sectional area of the diffuser pipe 40 in the second embodiment may become narrow step by step toward the terminal end from the air inlet end.

Further, the number of the diffuser pipes is not limited to four, and may be one or two or more than five. In terms of distributing the air to the whole region of the hollow fiber membrane, any number that allows a radial arrangement, namely three or more, is acceptable.

Moreover, the diffuser pipes may have a protruding section as a spacer to prevent adjacent hollow fiber membranes from contacting each other.

Furthermore, feed water and air may be fed to the diffuser pipes from the terminal section. In this case, it is recommended that base ends of respective diffuser pipes 40 be communicably connected to each other, and feed water and air be fed from the terminal section of at least one diffuser pipe 40 without providing the feed-water/gas feed and discharge pipe 38 that passes through the lower potting section 18.

The locations of the aeration holes are not particularly limited. However, because of the presence of the potting section below, in order to avoid interrupting air that flows from the aeration holes, it is preferable that the aeration holes be formed on the upper half of the diffuser pipes. When the aeration holes are formed on the lower half of the diffuser pipes, it is preferable that the holes be spaced from the potting section.

Furthermore, there is no particular limitation also to the number and shape of the aeration holes.

The aeration holes may be arranged in rows in the length direction of the diffuser pipe.

Moreover, in order to prevent the aeration holes from blockage due to foulants, fixture resin, or the like, banks may be provided around the aeration holes.

Furthermore, the hollow fiber membrane bundle is not limited to the examples in the drawings. In view of processability of the hollow fiber membrane module, for example, the bundle may be in the form of: a roll in which a bundle of the hollow fiber membranes comprising multiple strings thereof are wrapped around a shackle-like frame member; the knit fabric in which the hollow fiber membranes are used as crosswise threads; or the laminate in which multiple said knit fabrics are laminated. The hollow fiber membrane bundles may take any form as required by the process that is preferable for the hollow fiber membranes, the application of the hollow fiber membrane module, or the like.

[INDUSTRIAL APPLICABILITY]

The hollow fiber membrane module of the present invention is useful as the hollow fiber membrane module used in the filtration process of various fluids found in city water and sewage, electronic industry, food industry, beverage industry, pharmaceutical industry, fermentation industry, optical industry, medical treatment, precision machinery industry, and the like.

Claims

What is claimed is:

1. A hollow fiber membrane module comprising:

a hollow fiber membrane bundle including a plurality of hollow fiber membranes; a potting section in which respective upper and lower ends of the hollow fiber membrane bundle are put together by a resin in such a way that the hollow fiber membranes maintain opening at ends; and

a diffuser pipe arranged on or in the proximity of an upper surface of a lower side of the potting section,

wherein a cross-sectional shape of the diffuser pipe is a longer shape in a vertical direction than in a horizontal direction.

2. A hollow fiber membrane module comprising:

wherein a cross-sectional area of the diffuser pipe continuously and step-by-step becomes narrow toward a terminal end from an air inlet side that supplies air to the diffuser pipe.

3. A hollow fiber membrane module as set forth in claim 1 or 2 wherein the diffuser pipe is extended radially in three or more directions.

4. A hollow fiber membrane module as set forth in any one of claims 1 to 3 wherein part of the diffuser pipe is buried in the lower potting section.

5. A hollow fiber membrane module as set forth in any one of claims 1-4 wherein the diffuser pipe is also used as a feeding and exhausting pipe that feeds or discharges water to be treated.