JP2014104388A - Air diffusion device, and air diffusion method - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an air diffusion device, in which a large amount of fine air bubbles can be produced and the pressure drop of which hardly becomes larger even when a large amount of air is made to pass therethrough and to provide an air diffusion method in which the air diffusion device is used.SOLUTION: The tubular membrane type air diffusion device has a tubular base material and an elastic membrane which covers the tubular base material and on which many slits for producing fine air bubbles are formed. The slit has the length equal to or shorter than 0.5 mm and 200,000-600,000 pieces of slits are arranged on 1 mof the surface of the elastic membrane. The air diffusion method comprises a step of accomplishing passage of the air having the air passage amount per unit membrane area equal to or larger than 15 Nm/m/hr through the air diffusion device.

Description

  The present invention relates to a tube-type membrane diffuser installed in a tank of a sewage treatment facility or the like, and more particularly to an diffuser provided with a large number of slits in a diffuser membrane. The present invention also relates to an aeration method using the aeration device.

  Membrane diffusers using various rubbers are known as diffusers for water treatment. Since these bubbles have a small diameter, they have higher oxygen transfer efficiency than conventional diffusers and are less likely to be clogged, so they are used in many water treatments.

  The smaller the diameter of the bubbles diffused from the diffuser, the higher the oxygen transfer efficiency. For this purpose, it is necessary to reduce the hole diameter or the slit length. In this case, however, the pressure loss increases and the load on the blower increases.

Japanese Patent No. 4781302 (Patent Document 1) uses a tube-type membrane air diffuser having a slit length of 2 mm or less, a ventilation resistance of 10 kPa or less, and 13 Nm ³ / m ² / hr or less. A diffuser method for venting is described. In this air diffusion method of Patent Document 1, an increase in pressure loss is prevented by reducing the amount of air per membrane surface.

  FIG. 5 is a side view in which a part of the air diffuser (tube-type membrane diffuser) described in Patent Document 1 is a longitudinal section. An adapter 15 is connected to an opening on one end side of a resin or metal tube base material 11 constituting the tube type membrane diffuser 10. The adapter 15 has a first closing portion 16 and a second closing portion 17 that close the opening on the one end side, and a ventilation chamber 20 is formed between the first closing portion 16 and the second closing portion 17. ing.

  The second closing portion 17 has a vent pipe 18 having a first vent 18 a connected to an air supply source. A plurality of second vents 19 are formed on the peripheral wall 21 of the vent chamber 20. Yes. The opening 11a on the other end side of the tube base 11 is open.

  The entire outer surfaces of the tube base material 11 and the adapter 15 are covered with an elastic film (elastic film) 25. The elastic film 25 is a film having a thickness of about 1.0 to 3.0 mm made of ethylene propylene rubber or the like.

A large number of slits 26 are formed on the surface of the elastic film 25. The slit 26 has a length of 2 mm or less, preferably 1 mm or less, from the viewpoint of generating bubbles with a narrow distribution width and a uniform diameter as much as possible. The distribution density of the slits 26 is 1 to 100 pieces / cm ² .

  The elastic film 25 that covers the vicinity of the tube base opening 11a and the top thereof is fixed by tightening the metal band 31 from the outside. It is fixed by tightening with a metal band 32. The parts other than those fixed by the metal bands 31 and 32 are not fixed.

Japanese Patent No. 4781302

In order to operate the biological treatment tank at a high BOD volume load (for example, 2 kg / m ³ / d or more), it is necessary to increase the air flow rate. However, in the air diffusion method of Patent Document 1, the air flow rate per air diffuser is required. Therefore, it is necessary to increase the number of air diffusers and the cost is high. In addition, when space is limited, a sufficient number of air diffusers may not be installed.

  An object of the present invention is to provide an air diffuser capable of generating a large amount of fine bubbles and having a small increase in pressure loss even when the amount of ventilation is increased, and an air diffuser using the air diffuser. .

The air diffuser of the present invention is a tube-type membrane air diffuser having a tube base material and an elastic membrane formed with a large number of slits for generating fine bubbles covering the tube base material. Has a length of 0.5 mm or less, and 200,000 to 600,000 pieces are provided per 1 m ^{2 of} the film surface.

  The thickness of the elastic membrane is preferably 0.5 to 3 mm, and the length of the slit is preferably 0.3 to 0.5 mm.

The air diffusing method of the present invention is to ventilate the air diffusing device at a unit membrane area air flow rate of 15 Nm ³ / m ² / hr or more. The unit membrane area aeration rate is preferably 15 to 40 Nm ³ / m ² / hr.

The length of slits provided in the elastic membrane is 0.5 mm or less, and the number of slits per 1 m ^{2 of} the membrane surface is 200,000 to 600,000 pieces / m ² , so that the pressure loss is increased so much even at a high air flow rate. Fine bubbles can be generated, and high oxygen transfer efficiency can be obtained. By using polyurethane, EPDM or silicon rubber having a thickness of 0.5 to 3.0 mm as the elastic film, sufficient strength can be obtained even if the number of slits is increased.

It is slit arrangement | positioning explanatory drawing of the diffuser which concerns on embodiment. It is slit arrangement | positioning explanatory drawing of the diffuser which concerns on embodiment. It is slit arrangement | positioning explanatory drawing of the diffuser which concerns on embodiment. It is slit arrangement | positioning explanatory drawing of the diffuser which concerns on embodiment. It is a partial cross section figure of the diffuser of a prior art example.

  Hereinafter, embodiments will be described with reference to FIGS.

  Like the air diffuser of FIG. 5, the air diffuser of the present invention has a tube base material and an elastic film covering the tube base material, and a plurality of slits are provided in the elastic film. is there. As the tube base material, those having a diameter of about 50 to 120 mm and a length of about 500 to 1000 mm are suitable.

In the present invention, the slit has a length of 0.5 mm or less, preferably 0.3 to 0.5 mm, and 200,000 to 600,000, preferably 200,000 to 400,000 are provided per 1 m ² of the elastic membrane. It is done.

  The elastic membrane is preferably made of polyurethane, ethylene propylene rubber, or silicon rubber, and has a thickness of 0.5 to 3 mm, particularly 0.5 to 1 mm.

  The arrangement of the slits may be all parallel as shown in FIGS. 1 and 2, or may be provided in an intersecting manner as shown in FIGS. 1 indicates the length of the slit 2.

  1 and 2, all the slits 2 are arranged in the left-right direction (hereinafter sometimes referred to as X direction) in the figure. In FIG. 1, the slits 2 are arranged in a zigzag pattern, and in FIG. 2, the slits 2 are arranged in a grid pattern.

  In FIG. 3, the slits 2 in the X direction and the slits 3 in the Y direction (direction orthogonal to X) are alternately arranged in both the X direction and the Y direction.

  In FIG. 4, two X-direction slits 2 and 2 and two Y-direction slits 3 and 3 are paired, and X-direction pairs and Y-direction pairs are alternately arranged in the X-direction and Y-direction. Yes. In FIG. 4, two slits are paired, but three or more slits may be a set.

  Moreover, the arrangement | sequence of the slit shown in FIGS. 1-4 is an example, and this invention is good also as slit arrangements other than illustration.

In the aeration method of the present invention, the unit membrane area aeration rate (aeration rate per 1 m ^{2 of} membrane) is 15 Nm ³ / m ² / hr or more, preferably 15 to 40 Nm ³ / m ² / hr with respect to this aeration device. Ventilate so that it becomes the above. As a result, fine bubbles are generated from the air diffuser and an increase in pressure loss is also suppressed.

[Examples 1 to 3, Comparative Examples 1 to 5]
A cylindrical tube substrate having a diameter of 90 mm and a length of 760 mm is attached with an elastic membrane (membrane area 0.18 m ² , thickness 0.8 mm, material polyurethane) having the structure shown in Table 1 shown in FIG. Qi device was configured. Each air diffuser was immersed in a water tank filled with fresh water (tank capacity 1.6 m ³ (1 m × 0.4 m × depth 4 m)). Except for Comparative Example 4, the air flow rate was 6 Nm ³ / hr (33 Nm ³ / m ² / hr), and only Comparative Example 4 was vented with air flow rate of ² Nm ³ / hr (11 Nm ³ / m ² / hr). The pressure loss was measured.

  Table 1 shows the oxygen transfer efficiency (calculated from kLa), the pressure loss, the oxygen dissolution power efficiency determined from these, and the oxygen transfer amount.

  As shown in Table 1, in Examples 1 to 3, oxygen dissolution power efficiency and oxygen transfer amount 1.5 times or more were obtained as compared with Comparative Example 1 which has been widely used conventionally.

In Comparative Example 2 in which the length of the slit is 1 mm and Comparative Example 3 in which the number of slits is 150,000 / m ² , the performance is improved as compared with Comparative Example 1, but both remain at about 1.2 times. .

In Comparative Example 4 in which the ventilation amount was reduced, the power efficiency was higher than in Examples 1 to 3, but the oxygen transfer amount was reduced to about 60% of Comparative Example 1. Therefore, for example, when the biological treatment tank is operated at a BOD volume load of 2 kg / m ³ / d, oxygen supply becomes insufficient in consideration of a decrease in dissolution efficiency in sludge, and it is necessary to increase the number of diffusers. .

In Comparative Example 5 in which the number of slits was increased to 800,000 / m ² , the pressure loss was reduced, but the oxygen transfer efficiency was lowered, and the improvement in the oxygen transfer amount was only about 1.3 times that of Comparative Example 1. It was. In addition, when the manner in which air bubbles emerged from the air diffuser was observed, it was found that the generated air bubbles were associated with each other on the film surface because the slits were too dense.

2,3 Air diffuser 10 Air diffuser 20 Vent chamber 25 Elastic film

Claims (4)

In a tube-type membrane-type air diffuser having a tube base material and an elastic membrane formed with a large number of slits for generating fine bubbles covering the tube base material, the slit has a length of 0.5 mm. An air diffuser characterized in that 200,000 to 600,000 are provided per 1 m ^{2 of} membrane surface.   2. The air diffuser according to claim 1, wherein the elastic film has a thickness of 0.5 to 3 mm, and the slit has a length of 0.3 to 0.5 mm. A diffuser method for ventilating the diffuser according to claim 1 or 2 at a unit membrane area aeration rate of 15 Nm ³ / m ² / hr or more. The air diffusion method according to claim 3, wherein the unit membrane area aeration rate is 15 to 40 Nm ³ / m ² / hr.

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