Hollow fiber membrane module of immersing type

Details Hollow fiber membrane module of immersing type Hollow fiber membrane module of immersing type

1997-12-23

2003-10-07

Fortuna, Ana (Department: 1723)

Liquid purification or separation

Casing divided by membrane into sections having inlet

With membrane cleaning or sterlizing means

C210S321790, C210S321800, C210S456000, C210S636000

Reexamination Certificate

active

06630069

ABSTRACT:

BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to a separation membrane module having solid-liquid separating hollow fiber separation membranes used in the field of purification applications including the preparation of service water, drinking water, industrial water and pure water and polluted liquid treatment applications including removal of pollution from river water and sea water, treatment of waste water, night soil excrement and sewage water and condensation of slurry such as sludge, and a method for manufacturing such a separation membrane module.
Particularly, the present invention relates to a separation membrane module and a method for manufacturing such a separation membrane module, suitable for the treatment of a large amount of water.
Further, the present invention relates to water treating apparatus and method using such a separation membrane module.
2. Description of the Related Art
A hollow fiber separation membrane serves to cause liquid to flow through a tube wall having a great number of small holes to separate solid components or particles from the liquid. Material of the tube wall may be, for example, polyethylene, polypropylene, polysulfone, polyvinyl alcohol and their derivatives, 4-ethylene fluoride resin or cellulose acetate. An outer diameter of the hollow fiber separation membrane is 0.4 to 5 mm, for example, an inner diameter of the hollow fiber separation membrane is 0.3 to 4 mm, for example, and a diameter of each small hole is 0.01 to 5 &mgr;m, for example.
Since capacities required in a separation membrane module of a solid-liquid separation device are factors directly relating to water treatment amount and treatment efficiency such as wide separation area and good contact with fluid to be treated, for example, there have been investigated many hollow fiber membrane modules of a cylindrical type which comprises a bundle of hollow fibers arranged in a circle or concentric circles and has conventionally been used in the field of precision filtration applications. In this technique, the hollow fiber separation membranes are arranged in high density as much as possible and the number of hollow fibers are increased to obtain a condition that the hollow fibers are substantially in contact with each other, so that the surface area of the membranes is increased to increase the water treatment amount for each module.
However, if liquid to be treated having high density of suspended substance (for example, suspension in aeration tank used for sewage treatment process) is filtered by using such a hollow fiber separation membrane module, the suspended substance enters between the large number of hollow fiber separation membranes and is trapped therein. Consequently, the suspension cannot be supplied to the trapped zones, with the result that a plurality of hollow fiber separation membranes are apt to form stick-shaped bundles (such phenomenon is referred to as “inter-fiber clogging”). If such bundles are formed, since it is difficult for the liquid to be treated to enter into and be in contact with the interior of the bundle, the effective filtering area of the module is reduced, thereby worsening the filtering ability.
When such a hollow fiber separation membrane module (in which hollow fibers cohere (or stick) together into a mass) is periodically subjected to membrane surface cleaning or back washing, it is not easy to restore the function of the module whose hollow fibers once cohered together into a mass; in some cases, the hollow fiber separation membranes may also be damaged. This problem becomes noticeable particularly when highly polluted water or a large amount of water is treated.
In order to solve such a problem, modules having various configurations have been developed. For example, there has been proposed a water treating apparatus of immersing type in which a bundle of hollow fibers are arranged like a rattan blind in a flat plane to form a module and a plurality of modules are disposed side by side in a bath to form rough density sections, for example, refer to JP-A-5-220356 (Japanese Patent Laid-open), etc. However, also in such modules, since the arrangement of the bundle of the hollow fibers creates partial density sections and the hollow fibers are partially in contact with each other, the above problem cannot be solved completely.
The present invention aims to provide a hollow fiber separation membrane module and a method for manufacturing such a module, in which a polluted substance is hard to be deposited between hollow fiber separation membranes, and any increase in pressure difference, reduction of flow rate and inter-fiber clogging can be prevented for a long time.
Further, the present invention aims to provide a method for manufacturing a hollow fiber separation membrane module, in which, when the hollow fiber separation membrane module is manufactured, a great external force is not required, and the hollow fibers or bundles of hollow fibers can be interconnected in a spacial relation.
SUMMARY OF THE INVENTION
An object of the present invention is to provide a hollow fiber separation membrane module of immersing type having a plurality of hollow fiber separation membranes extending into liquid to be treated and a water collecting portion connected to ends of the hollow fiber separation membranes.
In the module according to the present invention, an inner cylindrical hollow portion of each hollow fiber separation membrane communicates with inner spaces of water collecting plates provided in the water collecting portions, and hollow fiber separation membrane strings comprised of one to seven hollow fiber separation membranes are spaced apart from each other so as not to be in contact with each other and are disposed in the water to be treated in a loosened condition.
Preferably, the module according to the present invention has the following arrangements. That is to say, (a) two water collecting portions are spaced apart from each other, and the hollow fiber separation membrane strings extend between the two water collecting portions and both ends of each hollow fiber separation membrane string are connected to the respective water collecting portions; (b) there is further provided a cleaning means a (
FIG. 1
or
6
) for removing substances accumulated on surfaces of the hollow fiber separation membrane strings from such surfaces; (c) the cleaning means includes a vibration means capable of vibrating the hollow fiber separation membrane strings; (d) the cleaning means has an air dispersing device having air dispersing plates disposed on the water collecting plates and adapted to supply bubbles into the liquid to be treated; (e) the cleaning means has a fluid pressure generating means so that pressurized fluid is discharged from discharge openings formed in the water collecting plates to flow the fluid toward the surfaces of the hollow fiber separation membrane; and (f) the water collecting plate has a plurality of water collecting openings, and the water collecting openings of one module can be connected to the water collecting openings of another module so that two or more modules are integrally connected to each other.
A concrete embodiment of the hollow fiber separation membrane module of immersing type is shown in
FIG. 1
, and supplementary explanation is made regarding the hollow fiber separation membrane module of immersing type according to the present invention. However, in
FIG. 1
, an example in which the hollow fiber separation membrane module of immersing type has a rectangular arrangement is illustrated, this example is merely used for explanation of the invention, and, thus, the present invention is not limited to such an example; however, a cylindrical arrangement as shown in
FIG. 6
can be applied to the present invention. Therefore, the present invention does not limit the configuration of the module.
Incidentally, in the following explanation, the hollow fiber separation membrane or the bundle of the hollow fiber separation membranes are also referred to merely as “hollow f

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