WO2005056167A1

WO2005056167A1 - A submerged hollow fiber membrane module

Info

Publication number: WO2005056167A1
Application number: PCT/KR2004/000215
Authority: WO
Inventors: Moo-Seok Lee; Kwang-Jin Lee; Yong-Cheol Shin; Seong-Hak Choi; Young-Tai Woo
Original assignee: Kolon Industries Inc
Current assignee: Kolon Industries Inc
Priority date: 2003-12-10
Filing date: 2004-02-05
Publication date: 2005-06-23
Anticipated expiration: 2006-06-10
Also published as: KR20050056293A; TW200518828A

Abstract

The present invention discloses a submerged hollow fiber membrane module which has a high reliability because it is adaptable on a small installation area, makes it easier couple and manufacture the module, and keeps a flux stably and prevents a membrane damage even in a strong air diffusion condition. The submerged hollow fiber membrane module comprises [I] a module upper header (4) having a filtrate water collecting portion (2) for collecting filtrate water filtered through hollow fiber membranes and a filtrate water outlet (3), [II] a module lower header (7) having an air injection port (5) and a plurality of air passages (6) which air injected through the air injection port (5) passes through and is ejected toward hollow fiber membranes (1), [III] a support pipe (9) whose both opposite ends are fixed in a buried state to the center of the module headers (4) and (7) by an adhesive (8) and fixes the two module headers (4) and (7) while keeping a predetermined distance between them, and [IV] a bundle of hollow fiber membranes (1) whose one ends are fixed to the inside of the module upper header (4) by an adhesive (8) with the ends (10) of hollow portions of the hollow fiber membranes being opened of the module lower header (7) by the adhesive (8).

Description

A SUBMERGED HOLLOW FIBER MEMBRANE MODULE

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a separation membrane module suitable for the field of treatment of water, such as waste water, sewage water, drinking water, etc., and more particularly, to a submerged hollow fiber membrane module which is easy to install and operate the module, has a small installation area, can stably maintain a flux through fouling prevention and has a high reliability of the quality of permeated water. A polymer separation membrane is being distributed to a wide variety of fields including the field of existing applications along with the development of its technology, especially, its demand is being increased in the field of water treatment along with the importance of the environment. A hollow fiber type membrane is generally such a module whose membrane is protected by a cylindrical case since it has an advantage in water treatment because of its high throughout per installation while its mechanical strength is low due to the characteristics of a porous membrane structure. In the module of such type, in case of wastewater treatment, as generally known, it is hard to remove foulants accumulated on surfaces of a membrane, and the permeability is lowered due to fouling. 2. Description of the Related Art In order to solve such a problem, submerged modules with no case had been devised. However, in a case that the strength of a membrane is not high enough, there may bring out the degradation of system reliability due to membrane damage. In this case, if air diffusion is not efficiently achieved, a fouling problem still occurs to thus increase the operation pressure and lower the flux. In order to minimize the loss of permeability of the submerged module, foulants accumulated on membranes have to be removed by air diffusion. For this, however, a strong air diffusion condition is required, thus there is a possibility that hollow fiber membranes are damaged. As a prior art submerged hollow fiber membrane module, Korean Registered Patent No. 22807 proposes a module fixed by developing a hollow fiber membrane in a conical form and folding it in a U shape in order to prevent the pollution of the membrane under a mild air diffusion condition. In this case, however, the volume of the module becomes larger and it is not easy to couple between modules for increasing a processing capacity from a structural viewpoint. Additionally, Korean Registered Patent No. 236921 proposes a submerged hollow fiber membrane module in which a hollow fiber membrane is not fold in a U shape but air injection port and a filtrate water outlet are connected to one portion of the module with both ends of the hollow fiber membrane being fixed in a I shape. Such module structure is inefficient to the arrangement of a water collecting pipe and an air injecting pipe in coupling a plurality of modules for increasing a processing capacity, and the filtrate water outlet and the air injection port coexist on one portion of the module, to thus decrease workability in the manufacture of a module. Further, in a case that the shape of a module is an I shape, this is a compact shape, so there is a merit that a large amount of water can be treated at a small installation area, while there is a big possibility that foulants would be accumulated intensively because a bundle of hollow fiber membranes are densely concentrated, thus an efficient air diffusion process has to be accompanied. During the air diffusion process, due to a direct impact applied to membranes by air, there may be occurred the degradation of quality of treated water by the damage of membranes.

SUMMARY OF THE INVENTION The present invention is designed in consideration of the problems of the prior art, and therefore the present invention to provide a submerged hollow fiber membrane module which has a high, reliability because it is adaptable on a small installation area, makes it easier couple and manufacture the module, and keeps a flux stably and prevents a membrane damage even in a strong air diffusion condition. For this, the present invention provides such a module which has the most compact structure and has both air injection port and filtrate water outlet completely separated into the upper and lower parts of the module, thereby providing convenient module coupling properties and module manufacturing properties, and which is designed so that hollow fiber membranes can receive a direct impact by air bubble so as to prevent the accumulation of foulants, and which prevents a membrane damage due to a strong air diffusion condition by using high strength hollow fiber membranes. To achieve the above object, there is provided a submerged hollow fiber membrane module according to the present invention, comprising: [I] a module upper header having a filtrate water collecting portion for collecting filtrate water filtered through hollow fiber membranes and a filtrate water outlet; [II] a module lower header having an air injection port and a plurality of air passages which air injected through the air injection port passes through and is blasted toward hollow fiber membranes; [III] a support pipe whose both opposite ends are fixed in a buried state to the center of the module headers by an adhesive and fixes the two module headers while keeping a predetermined distance between them; and [IV] a bundle of hollow fiber membranes whose one ends are fixed to the inside of the module upper header by an adhesive with the ends of hollow portions of the hollow fiber membranes being opened and the other ends thereof are fixed in a buried state to the inside of the module lower header by the adhesive. BRIEF DESCRIPTION OF THE DRAWINGS Other objects and aspects of the present invention will become apparent from the following description of embodiments with reference to the accompanying drawings in which: Fig. 1 is a cross sectional view of a submerged hollow fiber membrane module according to the present invention; and Fig. 2 is a schematic perspective view of the submerged hollow fiber membrane module according to the present invention.

DESCRIPTION OF THE PREFERRED EMBODIMENT Hereinafter, a preferred embodiment of the present invention will be described in more detail referring to the drawings. Fig. 1 is a cross sectional view showing a section state of a submerged hollow fiber membrane module according to the present invention. Fig. 2 is a schematic perspective view of the present invention, in which only one string of a hollow fiber membrane 1 is illmstrated for convenience. Firstly, the present invention includes a bundle of hollow fiber membranes 1 spread over in an I shape. One ends of the hollow fiber membranes 1 with hollow portions opened and the other ends thereof with hollow portions closed are fixed to a module upper header 4 and a module lower header 7, respectively, by an adhesive 8. In other words, as shown in Fig. 1 , one ends of the hollow fiber membranes 1 are fixed by penetrating through a fixing adhesive 8 inside a module upper header 4, thus making hollow portions opened. And, one ends of the hollow fiber membranes 1 are fixed in such a manner to form a water collecting portion 2 for collecting filtrate water filtered through the hollow fiber membranes 1 , thereby allowing the module upper header 4 to carry out a water collecting function. That is, filtrate water is spouted by a suction apparatus connected to a filtrate water outlet 3. At this time, the filtration function is provided just because the filtrate water is permeated through micro pores of a skin layer existing on the outer surfaces of the hollow fiber membranes 1. The other ends of the hollow fiber membranes 1 are fixed in a state that they are buried in the module lower header 7, thereby making hollow portions closed. At this time, the module lower header 7 is provided with an air injection port 5. Air is injected into the module lower header 7 through the air injection port 5, and the injected air is blasted toward the hollow fiber membranes through a plurality of air passages 6 penetrated through the fixing adhesive 8 of the module lower header 7 as shown in Fig. 1. The thusly blasted air rises along the hollow fiber membranes from the lowermost end of the module, and effectively removes (hereinafter, referred to as 'air diffusion') foulants accumulated on the surface of the hollow fiber membranes disposed at the lower part, central part and upper part of the module. Especially, a plurality of air passages are evenly arranged so as to efficiently shake the entire hollow fiber membranes, thereby maximizing air diffusion. And, since the blasting direction of air is the same as the longitudinal direction of the hollow fiber membranes, the risk of membrane damage is small in comparison with the method of vertically blasting to hollow fiber membranes. At this time, as the air passages 6, as shown in Fig. 2, can be used a plurality of air nozzles fixed to the module lower header 7 that is projected 0.5 to 5cm from a module potting surface 12 so as to flow air. The inner diameter of the air nozzles or the diameter of the air passages 6 is preferably 1 to 10cm. The air generated through the air passages 6 or the air nozzles is formed into relatively large air bubbles in the water, rises along the surfaces of the membranes to remove deposits, and provides vibration to the membranes to prevent the accumulation of foulants on the surface membranes. Therefore, the hollow fibers may beak because a load by air diffusion is continually applied to the hollow fiber membranes 1. Thus, it is preferable to use high strength hollow fiber membranes in which one string of the hollow fiber membranes 1 has a tensile strength greater than 1kg. The tensile strength is measured at an ambient temperature under the condition of a 10cm holding distance and a 2cm/ min crosshead speed by a tensile tester. The shape of the header of the submerged hollow fiber membrane module of the present invention is preferably a cylindrical shape or rectangular shape. When the submerged hollow fiber membrane module of the present invention is installed and used, air is injected into the air injection port 5 by an air injecting apparatus, and filtrate water is drawn by connecting a suction apparatus at the filtrate water outlet 3. The injection amount of air is 10 to 350£/min, more preferably 50 to 250£/min. As explained above, the present invention can prevent the accumulation of foulants on hollow fiber membranes because air is generated from the lowermost end of the module where the accumulation of foulants is concentrated and air bubbles rise vertically. Additionally, the water collecting portion and the air diffusion unit are separated into upper and lower parts, thereby simplifying the module manufacturing process and the module structure. That is, the module is designed in a manner that the water collection of filtered substances is achieved at the upper end and the air passages 6 communicate with the air injection port 5 at the lower end, thereby separating the function of the module into the upper and lower sides so as to achieve air supply. Furthermore, the present invention minimizes fouling and prevents the degradation of the reliability of the system due to the damage of membranes by enabling a strong air diffusion by using high strength hollow fiber membranes as membranes used for the module, considering that a I-shaped module is the most compact structure while it may cause a serious degradation of permeability due to the accumulation of polluted substances by the arrangement of the hollow fiber membranes densely collected. A conventional submerged hollow fiber membrane module is problematic in that a mounting area cannot be decreased, it is difficult to couple and manufacture the module, and membrane damage occurs in an air diffusion condition to degrade the reliability. The present invention is adaptable on a small installation area, makes it easier couple and manufacture the module as the water collecting function and the air diffusion function are separated into the upper and lower parts, undergoes no membrane damage even in a strong air diffusion condition, capable of keeping a flux stably, and is very high in reliability.

Claims

WHAT IS CLAIMED IS:

1. A submerged hollow fiber membrane module, comprising: [I] a module upper header having a filtrate water collecting portion for collecting filtrate water filtered through hollow fiber membranes and a filtrate water outlet; [II] a module lower header having an air injection port and a plurality of air passages which air injected through the air injection port passes through and is ejected toward hollow fiber membranes; [III] a support pipe whose both opposite ends are fixed in a buried state to the center of the module headers by an adhesive and fixes the two module headers while keeping a predetermined distance between them; and [IV] a bundle of hollow fiber membranes whose one ends are fixed to the inside of the module upper header by an adhesive with the ends of hollow portions of the hollow fiber membranes being opened and the other ends thereof are fixed in a buried state to the inside of the module lower header by the adhesive.

2. The module of claim 1 , wherein the ends of the hollow portions of the hollow fiber membranes fixed to the inside of the module upper header are disposed in parallel to a filtrate water discharge surface so as to form a water collecting space within the module upper header.

3. The module of claim 1, wherein the air passages have an air nozzle shape that are projected 0.5 to 5cm from a module potting surface and fixed to the module lower header.

4. The module of claim 3, wherein the inner diameter of the air nozzles is 1 to 10mm.

5. The module of claim 1, wherein the tensile strength of the hollow fiber membranes is 1kg/ strand or more.

6. The module of claim 1, wherein the shape of the module header is a cylindrical shape or a rectangular shape.