JPH08281083A - Immersion type membrane separation device - Google Patents

Abstract

PURPOSE: To increase an air lift circulation stream and to effectively peel off soiling of the membrane surface by expanding the lower part of an air lift cylinder of an immersion type membrane separation device in a truncated cone shape and enlarging the cross-sectional area in the direction facing downward. CONSTITUTION: A space of left and right side plates 22 at the lower half 21 of the air lift cylinder 11 is enlarged downwardly in a truncated cone shape and the cross-sectional area at the lower half is expanded in the direction facing downward. Plural air diffusion nozzles 24 for blowing air into the air lift cylinder 11 from the lower part are arranged so as to surround the lower edge of the air lift cylinder 11. Then, the air diffusion nozzles 24 can be easily attached and detached. Also the lower part of the air cylinder 11 becomes a turning back part of the air lift circulation stream, and the circulation flow rate of the lower part of the air lift cylinder 11 be increased by enlarging the lower half in a truncated cone shape.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a membrane element composed of a plurality of hollow fiber membranes, tubular membranes or flat membranes having a permeated water outlet in water in a treatment tank such as a biological reaction tank or a membrane dipping tank. By arranging the membrane modules standing in a row with a space in the front-back direction, the water head difference based on the water depth of the immersed membrane modules and the membrane pump at low energy by suction with a suction pump to obtain permeated water The present invention relates to a membrane separation device.

[0002]

2. Description of the Related Art FIG. 8 shows a plurality of flat sheet membrane elements 1 in which an air lift cylinder 11 is erected in the water of a treatment tank 10 to which raw water is supplied, and a permeated water outlet is provided in the upper half of the air lift cylinder.
Fig. 7 shows a conventional submerged membrane separation device in which a membrane module 13 in which 2 (Fig. 7A) are arranged in a row in the front-rear direction while keeping a flow path interval is arranged. An air diffuser 14 to which air is supplied from a blower B is arranged below the inside of the air lift cylinder. The air lift cylinder 11 has a quadrangular cross-sectional shape and has a constant cross-sectional area from the upper end to the lower end. When air is diffused from the air diffuser 14, a cross flow upward flow due to an air lift is generated in the flow path interval 15 between the opposed membrane surfaces of the flat sheet membrane element 12 constituting the membrane module in the air lift cylinder, and the gel state is formed on the membrane surface. The permeated water that permeates the membrane is obtained inside the flat sheet membrane element while preventing the adherents from being generated, and the permeated water is sucked by the pump P through the header pipe 17 connected to the outlet 16 of each flat sheet membrane element. And collect water.

[0003]

However, when the raw water contains a large amount of suspended matter at the same time as the polymer solute, if the operation is continued for a long time, the membrane surface and the flow path gap may be blocked. Therefore, it is necessary to periodically clean or remove the membrane module from the treatment tank in order to replace it.To do this, either attach the membrane module inside the air lift cylinder detachably or install the membrane module together with the air lift cylinder. Must be taken out of the processing tank, which is very troublesome and requires a complicated structure.

Furthermore, in order to circulate the raw water flowing upward in the air lift cylinder as a circulating flow, the upper end of the air lift cylinder and the water surface W of the treatment tank
A free zone 18 for turning back the flow of the raw water coming out from the upper end of the air lift cylinder must be provided between the and. Therefore, in order to inspect the membrane module immersed below the water surface W, it was necessary to lower the water level in the tank or pull up the membrane module each time.

[0005]

The present invention was developed in order to solve the above-mentioned problems of the conventional apparatus, and the invention of claim 1 is characterized in that bubbles are blown from below into the water in the processing tank. Immersion type in which an air lift tube to be inserted is erected, and a membrane module in which a plurality of membrane elements having permeate outlets are arranged in a row in the front-rear direction at a flow path interval in an upper part of the cylinder The membrane separation device is characterized in that the lower portion of the air lift cylinder is expanded in a skirt shape and its cross-sectional area is expanded downward. In the invention of claim 2, an air lift cylinder in which bubbles are blown from below is erected in the water in the treatment tank, and a plurality of membrane elements having an outlet for permeated water are provided in the upper part of the cylinder. In a submerged membrane separation device in which membrane modules are arranged in a row in a row with a flow path interval in the front-rear direction, on both side surfaces of the upper part of the air lift tube in which the membrane module is arranged, the membrane elements of the membrane module It is characterized in that an opening portion that communicates with the flow path interval in the direction is provided.

[0006]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS FIGS. 1, 2 and 3 are embodiments of the first aspect of the present invention,
4, 5 and 6 show an embodiment of claim 2 of the present invention, in which the same components as those of the conventional device of FIG. 8 are designated by the same reference numerals. In addition, the description will be made using a flat membrane element. In the embodiment of FIGS. 1 and 2, the cross-sectional area of the lower half portion is enlarged downward by expanding the space between the left and right side plates 22, 22 of the lower half portion 21 of the air lift cylinder 11 downward in a skirt shape. As is apparent from FIG. 2, the left and right side plates 22 are side plates whose upper half portions 22 'close the flow path intervals 15 between the flat sheet membrane elements from the left and right when viewed from above, and the side plates 23 in the front-rear direction, The space in the front-rear direction between the lower half portions of 23 is constant. That is, as shown in FIG. 2, the side plates 23 in the front-rear direction,
In 23, the distance between the upper and lower halves is constant at A1, while the distance between the upper and lower halves of the left and right side plates 22, 22 is B1.
, The maximum distance between the lower ends of the lower halves 22, 22 is B2 which is larger than B1. The air lift cylinder is not limited to the rectangular cylinder as in the illustrated embodiment, but may be a cylinder. In this case, the membrane element having the maximum width is arranged in the diametrical direction in the cylinder, and the membrane elements whose width is gradually narrowed away from the membrane element having the maximum width are arranged. Further, the skirt portion of the air lift cylinder may be a cylinder.

In the embodiment of FIG. 3, the space between the side plates 22 and 22 of the lower half portion 21 of the air lift cylinder 11 and the space between the lower half portions of the side plates 23 and 23 in the front-rear direction are also expanded downward in a skirt shape to form a sectional area. Is enlarged downward. Therefore, the air lift cylinder 1
The shape of the lower half portion 21 of 1 is a hood shape of a truncated square pyramid,
The distance between the upper halves of the side plates 23, 23 in the front-rear direction is constant at A1, whereas the maximum distance between the lower ends of the lower halves is A2 which is greater than A1, and the upper halves of the left and right side plates 22, 22. The distance between the parts is constant at B1, while the maximum distance between the lower ends of the lower half is B2 which is greater than B1.

The area ratio of the upper half part and the lower half part of the air lift cylinder is set so as to be equal to or less than the ratio of the total cross-sectional area of the flow passage intervals between the flat membrane elements of the membrane module and the superficial cross-sectional area. The respective cross-sectional areas are represented by the following symbols. Air lift cylinder upper half cross-sectional area (maximum): A1 * B1 Air lift cylinder lower half cross-sectional area (maximum): A1 * B2 (Fig. 2) Air lift cylinder lower half cross-sectional area (maximum): A2 * B2 (Fig. 3) Membrane module Empty column cross-sectional area (maximum): A1 * B2 Flat membrane module flow path interval cross-sectional area: nH * B1 where A1, B1, A2, and B2 are the maximum internal dimensions of the upper and lower halves of the air lift cylinder. Is shown. Also, for convenience, the outer dimensions of the membrane module are shown as the inner dimensions of the upper half of the air lift cylinder. H represents the width of the flow path interval formed between the flat films. n indicates the number of this flow path. The relation of the area ratio of the skirt portion of the air lift cylinder can be expressed as follows.

[Equation 1]

In any of the embodiments shown in FIGS. 1, 2 and 3, the lower end of the air lift cylinder 11 is located 50 to 150 mm below the lower end of the air lift cylinder 11 and outside the lower end of the air lift cylinder. A plurality of air diffuser nozzles 24 for blowing air from are arranged so as to surround the lower end of the air lift cylinder. The air diffuser nozzle 24 has an upper end connected to the header pipe 25.
The blower B is attached to the lower end of the air diffusing pipe 26 for the book, and the blower B supplies the air in the header pipe 25. Of course, the air diffuser is not limited to that of this embodiment, and may be an air diffuser like the conventional example of FIG.

As described above, the lower half of the air lift cylinder having the membrane module housed in the upper half is expanded into a skirt state, and the air diffuser nozzle 24 is provided on the outer periphery of the air lift cylinder, so that the air lift circulation flow is not reduced and the air lift circulation flow is reduced. The air nozzle can be easily attached and detached. That is, the upper end of the air diffuser 26 having the air diffuser nozzle 24 attached to the lower end is removed from the header pipe 25,
All you have to do is lift it above the surface of the water and wash it to remove the clogging.

The circulating flow inside the air lift cylinder can be expressed as follows in terms of the relationship between the amount of air blown inside the cylinder and the diffused water depth. Uo ∝ (h · Ug) ⁿ where Uo: Air lift cylinder internal rising velocity Ug: Air lift cylinder internal air blowing velocity h: Diffused water depth However, the cross flow velocity Um of the flow passage between flat membrane elements is simply It is not inversely proportional to the total cross-sectional area of the flow passage of the membrane module and the superficial cross-sectional area, and is not more than the reciprocal of the area reduction ratio due to the resistance of the flow passage. According to the embodiment of the present invention, by expanding the lower half portion of the air lift tube into the skirt state, the air amount can be increased to the same amount as Uo in the upper portion of the skirt, that is, the lower portion of the flat sheet membrane module. Here, this area ratio

[Equation 2] By this, the cross flow velocity Um can be provided by compensating for the flow velocity decrease due to the resistance of the flow passage interval.

Further, as described above, the air diffuser nozzle can be easily attached and detached by providing the air diffuser nozzle at a position 50 to 150 mm below the lower portion of the air lift cylinder and on the outer periphery thereof. Since the diffuser nozzle is not located inside the air lift tower, it can be easily taken out of the tank by raising and lowering the pipe 26 of the diffuser nozzle.

Further, the lower portion of the air lift cylinder serves as a folded-back portion of the air lift circulation flow, but the circulation velocity of the lower portion of the air lift cylinder can be increased by expanding the lower half portion in a skirt shape. For this reason, the air blown from the air diffusion nozzles on the outer periphery of the air lift cylinder can be effectively sent into the air lift cylinder while being added to the circulation flow velocity. That is,
By providing an air diffuser 50 to 150 mm below the lower portion of the air lift cylinder at which the circulation speed of the lower portion of the air lift cylinder is maximized, the air from the diffuser nozzle can be effectively put on the circulation flow speed and sent into the inside of the air lift cylinder. it can.

In the embodiment of claim 2 shown in FIGS. 4 and 5,
The air lift cylinder 11 has open portions 27, 27 on both side surfaces of the upper half portion.
And the flow path interval 15 in the front-back direction between the flat sheet membrane elements of the membrane module communicates with the open portions 27, 27. Therefore, the upper half part of the air lift cylinder that accommodates the membrane module only has the side plates 28, 28 in the front-rear direction, and the plurality of flat membrane elements constituting the membrane module are the side plates 2.
It is supported by a support rod provided between 8 and 28.

When the open portions 27, 27 communicating with the flow passage interval 15 between the flat membrane elements are provided on both side surfaces of the upper half of the air lift cylinder containing the membrane module as described above, the flow passage interval 15 is raised. The upward flow of the air lift is above the opening 2
The air can be circulated outside the air lift cylinder from 7, 27. Therefore, the upper end of the air lift cylinder can be located directly below the water surface W, and the free zone required by the conventional device to generate the air lift circulation flow can be eliminated.
In other words, the free zone is necessary to turn the upward flow of water in the air lift cylinder into a downward flow outside the air lift cylinder to generate an air lift circulation flow. If the free zone is located just below the water surface and the free zone is abolished, in order to generate the air lift circulation flow, the water flow that flows upward in the air lift cylinder must be raised above the water surface, which requires a large amount of air and energy. Consumption is large. However, if the open portions 27 communicating with the flow path intervals 15 between the flat sheet membrane elements are provided on both side surfaces of the upper half of the air lift cylinder as in the present invention, the upward flow in the air lift cylinder is outward from the open portions. Since the air lift circulation flow is generated, the free zone can be eliminated and the upper end of the air lift cylinder can be positioned immediately below the water surface, which facilitates inspection of the membrane module.

Further, the upward flow of the air lift rising in the flow path interval 15 changes its direction toward the open portions 27, 27 within the flow path interval, so that the flat membrane is formed by the increased flow velocity and the turbulent flow that changes the direction. Effectively removes dirt adhering to the film surface of the element.

In FIG. 6, as described in claim 1, the lower half portion 21 of the air lift cylinder 11 is expanded downward in a skirt shape to expand the cross-sectional area downward, and the aeration nozzle 24 is moved to the lower end of the air lift cylinder 11. Provided on the outer periphery below the membrane module 13
The open part 2 communicating with the flow path gap 15 between the flat sheet membrane elements as described in claim 2 on both side surfaces of the upper half part accommodating the
This is an example in which 7, 27 are provided. This embodiment is claim 1.
The effect of being able to efficiently generate the air lift circulation flow which is the feature of the above, and at the same time, to increase the circulation flow velocity of the lower part of the air lift cylinder, and the feature of claim 2 are that the membrane module is arranged just under the water surface for efficient circulation. In addition to generating a flow, a turbulent flow is generated, and dirt on the film surface can be effectively separated.

In the illustrated embodiment, the membrane element is shown in FIG.
Although the flat membrane element shown in (a) has been described, the membrane element is not limited to the flat membrane element, and as shown in FIG. 7B, a large number of hollow fiber membranes are provided between the left and right spacers 1 and 1 which also serve as water collecting channels. Alternatively, the tubular membranes 2 and 2 may be laterally stretched to form a rectangular shape.

[0019]

According to the first aspect of the present invention, by expanding the lower portion of the air lift cylinder in which the membrane module is housed into the skirt state, the air lift circulation flow can be increased and the dirt on the membrane surface can be effectively removed. According to the second aspect of the present invention, the membrane module can be arranged immediately below the water surface to efficiently generate a circulation flow, and generate a turbulent flow to effectively remove dirt on the membrane surface.

[Brief description of drawings]

FIG. 1 is a sectional view of an embodiment of the invention of claim 1;

FIG. 2 is a plan view of the air lift cylinder of FIG. 1 viewed from above.

FIG. 3 is a plan view of an air lift cylinder of another embodiment of the invention of claim 1 as seen from above.

FIG. 4 is a side view of an embodiment of the invention of claim 2;

FIG. 5 is a front view of FIG. 4;

FIG. 6 is a front view of another embodiment of the invention of claim 2;

FIG. 7 is a cross-sectional view of a conventional device.

FIG. 8A is a perspective view of a flat sheet membrane element.
(B) is a perspective view of a membrane element including a hollow fiber membrane or a tubular membrane.

[Explanation of symbols]

 10 Treatment Tank 11 Air Lift Cylinder 12 Flat Membrane Element 13 Membrane Module 15 Channel Distance 18 Free Zone 21 Lower Half of Air Lift Cylinder 22 Left and Right Side Plates of Lower Half of Air Lift Cylinder 23 Side Plates Front and Back of Lower Half of Air Lift Cylinder 24 Air diffuser 27 Open part 28 Front and rear side plates of the upper half of the air lift cylinder

Claims (2)

[Claims] 1. An air lift cylinder in which air bubbles are blown from below is erected in water in a treatment tank, and a plurality of membrane elements having permeated water outlets are flown in the front-back direction in the upper part of the cylinder. An immersion-type membrane separation device in which membrane modules arranged in a row with a road spacing are arranged, wherein the lower part of an air lift cylinder is expanded in a skirt shape and its cross-sectional area is expanded downward. . 2. An air lift cylinder in which air bubbles are blown from below is erected in the water in the treatment tank, and a plurality of membrane elements having permeated water outlets are flown in the front-back direction in the upper part of the cylinder. In a submerged membrane separation device in which membrane modules are arranged in a row with a space between them, in the both side surfaces of the upper part of the air lift tube in which the membrane module is arranged, the flow path in the front-back direction of the membrane element of the membrane module. An immersion-type membrane separation device, characterized in that an opening portion communicating with the space is provided.