KR100893308B1 - Membrane module for immersed operation - Google Patents

Abstract

The present invention relates to a fiber bundle (1) of a plurality of hollow fiber membranes (2) and a headpiece (3) whose open ends are cast in the headpiece (3) and surrounded by liquid to be filtered during immersion operation. Permeate collection chamber (4) having at least one permeate outlet (5) for permeate discharged from the interior of the hollow fiber membrane (2), and the headpiece (3). A membrane module operating in an immersed state, having a gas supply portion 6 with a pipe 7 guided by it. The pipe 7 is terminated inside the fiber bundle 1, while having a gas outlet 8 for the gas medium, after the gas medium has transitioned from the pipe to the liquid to be filtered, the hollow of the fiber bundle 1 It rises mainly as a bubble between the fiber membranes 2. According to the invention, the fiber bundle 1 is divided into a plurality of zones 11 each comprising a group of hollow fiber membranes 2. A free space 12 is maintained between these zones 11, which extend from the pipe 7 to the outer periphery of the headpiece 3, so that the fiber bundles adjacent to the headpiece 3 ( Promote the inflow of liquid to be filtered into the foot region of 1).

Description

Submerged Membrane Modules {MEMBRANE MODULE FOR IMMERSED OPERATION}

The present invention is a membrane module that operates in a immersed state,

A fiber bundle of a plurality of hollow fiber membranes whose open ends are cast into a headpiece and are surrounded by a liquid to be filtered during immersion operation;

A permeate collection chamber adjacent the headpiece and having at least one permeate outlet for permeate discharged from the interior of the hollow fiber membrane;

Gas supply with pipe guided through the headpiece

Wherein the pipe terminates inside the fiber bundle, while having a gas outlet for the gas medium, the gas medium rises primarily as bubbles between the hollow fiber membranes of the fiber bundle after transitioning from the pipe to the liquid to be filtered. To such a membrane module.

Hollow fiber membranes generally refer to capillary membranes having a length greater than 1 m and a diameter in the range between 100 μm and 5 mm. In immersion operation, the membrane module is immersed in a basin with the liquid to be filtered and the hollow fiber membrane is usually oriented vertically in the liquid. In the membrane module operating in the immersion operation, the permeate is pumped from the permeate collection chamber. As a result, a pressure lower than the pressure of the liquid on the outside of the hollow fiber membrane is maintained in the permeate collection chamber.

Membrane modules with the features described at the outset are known from DE-C 100 45 227. The hollow fiber membrane has one end and is cast formed in the headpiece in the other end individually closed. The permeate collection chamber, together with the headpiece and gas supply, forms a foot part that can be mounted to the frame and soaked in a bath containing liquid to be filtered. The hollow fiber membranes stand in the liquid to be filtered similarly to seaweeds and can perform relative motion with each other. Only excessive movement of the fiber bundles is suppressed through the lateral fiber retainer. When the membrane module is in operation, dirt is deposited on the membrane surface of the hollow fiber membrane. Through the replenishment of air introduced into the fiber bundle through the gas supply pipe, the liquid to be filtered and the hollow fiber membrane are brought into motion, and dirt held on the hollow fiber membrane can be transported away. However, known methods are not sufficient to permanently prevent the deposition of sludge in the foot area of the fiber bundle. The foot area is a fiber bundle region adjacent to the headpiece, in which the hollow fiber membrane can only move to a limited extent by being fixed at the end side. The sludge deposition, starting at the foot of the membrane module, continues upwards, and over time, a rather large portion of the fiber bundle is completely covered with sludge and can no longer be cleaned cleanly through a strong gas supply. do. The replenished air passes through the area of the fiber bundle where the sludge deposition increases as a result of the faster sludge deposition in the fiber bundle. The earlier the sludge deposition in the fiber bundle begins, the greater the flow of permeate, which leads to local dewatering of the sludge.

It is known from WO 97/06880 a membrane module which operates in an immersed state, in which a fiber bundle of hollow fiber membranes is fixed between two headpieces. The face of the two headpieces occupied by the hollow fiber membrane is divided into a plurality of zones, and free space is maintained between these zones. This free space is used to arrange a gas distributor with a channel having a gas outlet adjacent to the pipe. Air usually rises in the free space of the fiber bundle, causing vortexing of the liquid to be filtered. A similar configuration for membrane modules is disclosed in JP-A 07/185 268, which is not used for immersion operation but in jacket pipes through which the liquid to be filtered flows. The deposition of sludge in fiber bundles is permanently unavoidable, even with the configurations known from WO 97/06880 and JP-A 07/185268.

The present invention is based on the task of providing a membrane module suitable for operation in a submerged state with a low sludge deposition tendency. Even if the amount of dirt is high and the permeability of the hollow fiber membrane is high, sludge deposition in the foot area of the fiber bundle should be prevented.

The above object of the present invention is a membrane module having a configuration described in the beginning, wherein the fiber bundle is divided into a plurality of zones each comprising a group of hollow fiber membranes, free space is maintained between the zones, this free The space is solved by extending from the pipe to the outer circumference of the headpiece, promoting the inflow of liquid to be filtered in the foot region adjacent the headpiece. A gaseous medium, mainly air, is supplied into the interior of the fiber bundle, creating a flow of flow through the rise of gas bubbles. According to the present invention, liquid from the periphery of the fiber bundle can flow through the free space in the foot region of the fiber bundle. This flow affects the area between the hollow fiber membranes in these zones, preventing the sludge from starting to accumulate there. Sediments can be sent away in a timely and efficient manner. The interaction of the central gas supply inside the fiber bundle, combined with the free space in the fiber bundle extending star or radially from the pipe to the outer circumference of the headpiece, is very likely to cause sludge deposition in the foot area of the fiber bundle. Prevent in an efficient manner. The headpiece can be configured as a cylindrical sleeve, suitably the pipe of the gas supply is arranged on the axis of the cylinder.

In a preferred embodiment of the invention, the headpiece has a star insert surrounding the pipe, which divides the face of the headpiece occupied by the hollow fiber membrane into a plurality of zones, between the zones. Form free space. The star insert is cast molded into the headpiece with hollow fiber membranes, which are then wholly or partially surrounded by the cast forming material. The insert has a radial or spirally curved web extending from the pipe or hub surrounding the pipe to the outer circumference of the headpiece. These webs are appropriately rounded or inclined at the top.

To produce the membrane module, a fiber bundle is inserted into the headpiece and the free space between the headpiece and the hollow fiber membrane is cast molded with a cast molding resin. Introduction of the fiber ends of the hollow fiber bundles into the headpiece can be facilitated by appropriate improvements in the insert. A suitable improvement of the teaching according to the invention is that the height decreases as the insert goes from inside to outside, the core portion of the insert adjacent to the pipe protrudes above the jacket of the headpiece at the face, and the jacket side connection end of the insert is That the jacket of the piece is arranged to recess in the space surrounded by the jacket of the headpiece to form an edge protruding from the top.

When introducing a bundle of hollow fiber membranes into the headpiece, the fiber ends that meet the insert are deflected outwards, causing adjacent fibers to be displaced in the direction of the jacket side edges to make the bundle compact. In this way, the hollow fiber membranes are densely packed in the zones and are evenly distributed throughout. Suitably the edge has an inner surface that is conically inflated upwards.

As a further refinement, the present invention teaches to provide a star insert with an opening for injecting a cast molding material distributed under the star insert to tightly surround the hollow fiber membrane. The star insert is a molded plastic part of plastics, suitably providing sound adhesion to the cast molding material. The star insert and the cast molding material used for the cast molding of the hollow fiber membrane may be made of the same material.

According to a preferred embodiment of the present invention, the gas outlet of the pipe is arranged at a short distance from the headpiece in the foot region of the fiber bundle, so that the gas medium is discharged in a generally uniform distribution from the circumference of the pipe. This can be realized in structurally different ways. Within the scope of the present invention, the pipe is closed at the top and has a plurality of openings on the jacket side. In a preferred embodiment a cap closed at the top is arranged in the pipe, the pipe and the cap forming a flow space for the gas medium which is open at the bottom of the cap. This flow space forms a ring-shaped gap from which the gaseous medium is discharged in a uniform distribution. An air cushion in the flow space prevents the ingress of liquid into the pipe, further preventing the deposition of dirt in the pipe. Within the scope of the teachings according to the invention, the pipe may also have an axial outlet opening embodied as a nozzle designed for example in the form of a venturi nozzle. The flow of air flowing out at high speed has a significant suction effect on the surrounding liquid.

According to a preferred embodiment of the present invention, the hollow fiber membrane is individually closed at the end facing away from the headpiece, and the closed end of the hollow fiber membrane is free to move in the liquid. However, within the scope of the present invention, fiber bundles may also be secured between two headpieces and permeate collection chambers may be connected to both headpieces.

The invention is now described with reference to the drawings, which show merely exemplary embodiments.

1 is a longitudinal section through the membrane module,

FIG. 2 is a longitudinal cross section through the headpiece of the membrane module shown in FIG. 1, FIG.

3 is a cross-sectional view taken from the cross-section I-I of FIG. 2,

4 is another embodiment of a headpiece in plan view,

FIG. 5 is a longitudinal cross-sectional view of the headpiece shown in FIG. 4, more specifically, while the cast molding material is applied during the manufacturing process of the headpiece, FIG.

6 is a longitudinal cross-sectional view of another embodiment,

7 is a view showing a membrane module according to the prior art corresponding to FIG.

8a and 8b is a view comparing the deposition of dirt in the membrane module according to the present invention and the membrane module according to the prior art.

The membrane module shown in the figure is intended for immersion operation. Its basic structure is connected to the head bundle 3 and the fiber bundle 1 of the plurality of hollow fiber membranes 2 whose open ends are cast molded into the headpiece 3 and surrounded by the liquid to be filtered during the immersion operation. On the other hand, a gas having a permeate collection chamber 4 having at least one permeate outlet 5 for permeate flowing out from the interior of the hollow fiber membrane and a pipe 7 guided by the headpiece 3. It consists of a supply part 6. The pipe 7 is terminated inside the fiber bundle 1 while having a gas outlet 8 for the gas medium, which mainly passes after the fiber bundle 1 is transferred to the liquid to be filtered. It rises as a bubble between the hollow fiber membranes 2). Air is usually used as the gas medium.

2 and 3, the headpiece 3 has a star insert 9 surrounding the pipe 7, which insert 9 is a headpiece occupied by the hollow fiber membrane 2. It can be seen that the face 10 of 3) is divided into a zone 11 and a free space 12 between the zones 11. The free space 12 between the zones 11 extends from the pipe 7 to the outer periphery of the headpiece 3 so that the foot area F of the fiber bundle 1 adjacent the headpiece 3 is present. ) To facilitate the introduction of the liquid to be filtered. The foot area F means the area of the fiber bundle 1 adjacent to the headpiece 3, in which the fibers are only able to perform a minimum relative movement with respect to each other because their ends are fixed. On the other hand, the deposition of dirt or sludge usually starts. The fiber zone, represented by the foot region F, extends over about 200 mm.

The headpiece 3 is configured as a cylindrical sleeve and is formed as a separate part fitted in the permeate collection chamber 4 in this embodiment. However, the headpiece 3 may also be molded in the permeate collection chamber 4. The pipe 7 of the gas supply 6 is arranged in the cylindrical axis of the sleeve and is surrounded by the hollow fiber membrane 2 of the fiber bundle 1. The star insert 9 of the headpiece 3 has a radial web 13 extending from the hub 14 surrounding the pipe 7 to the outer periphery of the headpiece 3. At the top, the web 13 is rounded or inclined. In addition, from the illustration of FIG. 2, the insert 9 decreases in height from inner to outer, so that the core portion of the insert 9 adjacent to the pipe protrudes above the jacket of the headpiece 3 from this side, The jacket side connecting end is arranged to concave into the space surrounded by the jacket of the headpiece 3 so that the jacket of the headpiece 3 forms an edge 15 protruding from the top. Edge 15 has an inner surface that expands conically upward. The aforementioned shapes of the headpiece 3 and the insert 9 make it easy to introduce the fiber bundle 1 into the headpiece 3 during the manufacture of the module.

The star insert 9 is cast molded in the headpiece 3 with the hollow fiber membrane 2 in place, and then in whole or in part surrounded by the cast molding material. In the embodiment shown in FIG. 4, the star insert 9 is provided with an opening 18 for injecting a cast molding material which spreads under the insert 9 to tightly surround the hollow fiber membrane 2. The cast molding process is shown in FIG. The star insert 9 is designed as a molded plastic part and is made of a plastic having a sound adhesion affinity that is satisfactory to the cast molding material. The cast molding material used for the cast molding of the star insert 9 and the hollow fiber membrane 2 may also be made of the same material.

The gas outlet 8 of the pipe 7 is arranged at a short distance from the headpiece 3 in the foot region of the fiber bundle 10 so that the gas medium can be discharged in a generally uniform distribution from the circumference of the pipe 7. It is supposed to be. The shape of the preferred structure is shown in FIG. A cap 16 closed at the top is disposed on the pipe 7 so that the pipe 7 and the cap 16 form a flow chamber for the gaseous medium which opens at the lower end of the cap. In the embodiment of FIG. 6, the pipe 7 has an axial outlet opening configured as a nozzle, for example a venturi nozzle 19. The gaseous medium exiting at high flow rates has a jet pump effect on the surrounding liquid.

Test result:

For testing, two membrane modules constructed according to the invention and modules according to the prior art were operated under the same conditions. Fig. 3 shows the fiber distribution of the membrane module according to the invention, and Fig. 7 shows the fiber distribution of the membrane module according to the prior art used as a comparative example. These membrane modules are no different in terms of gas supply.

The liquid to be filtered had a 3.5 g / l solid component (dry matter), which increased to 12 g / l within 24 hours. The membrane module was operated with varying permeate flow over a period of nine days with the same aeration.

The following permeate flow rate was set as the change in pressure difference across the membrane.

Days Permeate Flow Rate (ℓ / ㎡ / h)

14 L / m2 / h in 1-2 days

3 to 5 days 17 L / m2 / h

6 days 20 ℓ / ㎡ / h

7 days 22 ℓ / ㎡ / h

8 to 9 days 25 L / m 2 / h

Even after 4 days with the minimum permeate flow rate, a tendency to increase sludge deposition was observed in the fiber bundles of the module of the comparative example. When the flow rate of the permeate increased, the sludge deposition in the module of the comparative example proceeded rapidly, whereas no deposit of dirt appeared in the fiber bundle of the membrane module according to the present invention. 8A and 8B show the fiber bundles after the end of the nine day test run. In the fiber bundles (A) of the two membrane modules according to the invention no significant dirt deposits were seen in the foot area, while in the fiber bundles (B) of the comparative module, they were covered with sludge from the bottom to the top.

Claims (13)

A membrane module for immersion operation that can be lowered into a water bath containing a liquid to be filtered, A fiber bundle 1 of a plurality of hollow fiber membranes 2 with an open end cast in the headpiece 3 and surrounded by a liquid to be filtered during immersion operation; A permeate collection chamber (4) connected to the headpiece (3) and having at least one permeate outlet (5) for permeate exiting from the interior of the hollow fiber membrane (2); Gas supply 6 with pipe 7 guided through the headpiece 3 The pipe 7 terminates inside the fiber bundle 1, while having a gas outlet 8 for the gas medium, after the gas medium has transitioned from the pipe to the liquid to be filtered, the fiber bundle The membrane module which mainly rises as a bubble between the hollow fiber membranes (1) of (1), The fiber bundle 1 is divided into a plurality of zones 11 each comprising a group of hollow fiber membranes 2, between which the star-shaped or radial free spaces 12 are maintained. The free space 12 extends from the pipe 7 to the outer periphery of the headpiece 3 to facilitate the introduction of liquid to be filtered into the foot area of the fiber bundle 1 adjacent to the headpiece 3. Membrane module, characterized in that. Membrane module according to claim 1, characterized in that the headpiece (3) is configured as a cylindrical sleeve and the pipe (7) of the gas supply (6) is arranged on the axis of the cylinder. 3. The headpiece (3) according to claim 1 or 2, wherein the headpiece (3) has a star insert (9) surrounding the pipe (7), which star insert (9) occupies the hollow fiber membrane (2). Membrane module, characterized by dividing the face (10) of the headpiece (3) into a plurality of zones (11), forming a free space (12) between the zones (11). 4. The star insert (9) of the headpiece (3) according to claim 3, wherein the star insert (9) of the headpiece (3) extends from the pipe (7) or from the hub (14) surrounding the pipe (7) to the outer circumference of the headpiece (3). Membrane module, characterized in that it comprises a web or a spirally curved web (13). 5. The membrane module according to claim 4, wherein the upper part of the web is rounded or inclined. 4. The insert (9) according to claim 3, wherein the insert (9) decreases in height from inside to outside, and the core portion of the insert (9) adjacent the pipe (7) protrudes from the face above the jacket of the headpiece (3). The jacket side connection end of the insert 9 is arranged to be recessed into the space surrounded by the jacket of the headpiece 3 so that the jacket of the headpiece 3 forms an edge 15 protruding from the top. Membrane module. Membrane module according to claim 6, characterized in that the edge (15) has an inner surface which expands conically upward. 4. The star insert (9) according to claim 3, characterized in that the star insert (9) comprises an opening (18) for injecting a cast molding material which spreads under the insert (9) to tightly surround the hollow fiber membrane (2). Membrane module. 4. The membrane module according to claim 3, wherein the star insert (9) and the cast molding material used for the cast molding of the hollow fiber membrane (2) are made of the same material. 3. The gas outlet 8 according to claim 1, wherein the gas outlet 8 is arranged at a short distance from the headpiece 3 in the foot region of the fiber bundle 1. Membrane module, characterized in that configured to be discharged in a substantially uniform distribution from the circumference of the. 11. The flow space 17 for the gas medium according to claim 10, wherein a cap 16, which is closed at the top, is arranged on the pipe 7, wherein the pipe 7 and the cap 16 are open at the lower end of the cap. Membrane module, characterized in that to form a. Membrane module according to claim 10, characterized in that the pipe (7) has an axial outlet opening consisting of a nozzle. The membrane module according to claim 12, wherein the outlet opening of the pipe (7) is configured as a venturi nozzle (19).

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