TWI601696B - Diffusion method - Google Patents

Description

Gas diffusion method

The present invention relates to a tubular membrane type diffusing device provided in a tank for a sewage treatment facility or the like, and particularly relates to a diffusing device having a plurality of slits in a diffusing film. Further, the present invention is related to a gas diffusion method using the air diffusing device.

The air diffusing device for water treatment is well known as a membrane type diffusing device using various rubbers. These, because of the small diameter of the bubble, compared to the conventional air diffusing device, because of the high oxygen mobility and the difficulty in clogging, it is utilized in many water treatments.

The smaller the diameter of the air bubbles scattered by the air diffusing device, the higher the oxygen moving efficiency. Therefore, the aperture or the slit length must be reduced, however, at this time, the pressure loss becomes large, and the burden of the blower is increased.

Japanese Patent No. 4,871,302 (Patent Document 1) discloses a tubular membrane type air diffusing device having a slit length of 2 mm or less, and the ventilation resistance is 10 kPa or less, and the ventilation is performed at 13 Nm ³ /m ² /hr or less. Gas diffusion method. The air diffusion method of Patent Document 1 prevents the increase in pressure loss by reducing the amount of ventilation per unit film surface.

Fig. 5 is a longitudinal sectional side view showing a part of a diffusing device (tube type membrane diffuser) described in Patent Document 1. The joint 15 is connected to one end side opening of the resin or metal pipe base material 11 constituting the tubular film diffuser 10. The joint 15 has a first closing portion 16 and a second closing portion 17 that close the opening on the one end side, and a ventilating chamber 20 is formed between the first closing portion 16 and the second closing portion 17.

The second closing portion 17 is provided with a ventilation pipe 18 having a first ventilation port 18a connected to an air supply source, and a plurality of second ventilation ports 19 are formed in the peripheral wall 21 of the ventilation chamber 20. The other end side opening portion 11a of the tube base material 11 is in an open state.

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

On the surface of the elastic film 25, a plurality of slits 26 are formed. The distribution width of the slits 26 is preferably 2 mm or less in length, and preferably 1 mm or less from the viewpoint of generating bubbles having a uniform diameter as much as possible. The distribution density of the slits 26 is 1 to 100 strips/cm ² .

The elastic film 25 covering the vicinity of the tube substrate opening portion 11a and the upper portion thereof is fixed by the metal tape 31 from the outside, and covers the first closing portion 17 of the joint and the elastic film 25 thereon. The outer side is fixed by a metal band 32. The portion fixed by the metal strips 31, 32 is not fixed.

[Previous Technical Literature] [Patent Literature]

[Patent Document 1] Japanese Patent No. 4,801,302

In order to operate the biological treatment tank with a high BOD volumetric load (for example, 2 kg/m ³ /d or more), the amount of ventilation must be increased. When the gas diffusion method of Patent Document 1 is used, the ventilation amount of the unit air diffusing device is small, The number of gas devices must be increased to increase costs. In addition, when there is space limitation, sometimes a sufficient number of air diffusers cannot be set.

An object of the present invention is to provide a diffusing device which can generate a large amount of fine air bubbles and which has a small amount of ventilation, and which has a small increase in pressure loss, and a diffusing method using the diffusing device.

The air diffusing device of the present invention is a tubular film type air diffusing device having a tube base material and an elastic film formed on the tube base material and forming a plurality of slits for generating fine bubbles, and the ventilation amount per unit membrane area is A method of diffusing air for ventilation of 15 Nm ³ /m ² /hr or more is characterized in that the slits are arranged in a staggered manner and have a length of 0.5 mm or less, and 200,000 to 600,000 sheets per 1 m ^{2 of the} film surface.

Preferably, the length of the slit is 0.3 to 0.5 mm.

The ventilation per unit membrane area is preferably 15 to 40 Nm ³ /m ² /hr.

The gap length of the elastic film is 0.5 mm or less, and the number of slits per 1 m ^{2 of the} film surface is 200,000 to 600,000 pieces/m ² , and even if the ventilation volume is high, the pressure loss does not rise too much, and fine bubbles can be generated. In turn, high oxygen mobility is obtained. By using a polyurethane having a thickness of 0.5 to 3.0 mm, EPDM, or a silicone rubber as an elastic film, even if the number of slits is large, a sufficient strength can be obtained.

2‧‧‧ gap

3‧‧‧ gap

10‧‧‧ tubular membrane diffuser

11‧‧‧Tube substrate

11a‧‧‧ Opening

15‧‧‧Connector

16‧‧‧1st occlusion department

17‧‧‧2nd occlusion department

18‧‧‧ ventilation pipe

18a‧‧‧1st vent

19‧‧‧2nd vent

20‧‧‧Ventilation room

21‧‧‧Week wall

25‧‧‧elastic film

26‧‧‧ gap

31‧‧‧Metal strip

32‧‧‧Metal strip

Fig. 1 is an explanatory view showing a slit arrangement of a diffusing device of an embodiment.

Fig. 2 is an explanatory view showing a slit arrangement of the diffusing device of the embodiment.

Fig. 3 is an explanatory view showing a slit arrangement of the diffusing device of the embodiment.

Fig. 4 is an explanatory view showing a slit arrangement of the diffusing device of the embodiment.

Fig. 5 is a partial sectional view showing a conventional air diffusing device.

Hereinafter, an embodiment will be described with reference to FIGS. 1 to 4 .

The air diffusing device of the present invention has a tube base material and an elastic film covering the tube base material, and a plurality of slits are disposed in the elastic film, similarly to the air diffusing device of the fifth embodiment. The tube substrate is preferably 50 to 120 mm in diameter and 500 to 1000 mm in length.

In the present invention, the length of the slit is 0.5 mm or less, preferably 0.3 to 0.5 mm, and the elastic film is provided with 200,000 to 600,000 sheets per 1 m ^{2 of the} film surface, preferably 200,000 to 400,000.

The elastic film is composed of polyurethane, ethylene propylene rubber, or silicone rubber, and has a thickness of 0.5 to 3 mm, especially 0.5 to 1 mm. good.

The slits may be arranged in parallel as shown in Figs. 1 and 2, or may be arranged in a cross shape as shown in Figs. 3 and 4 . L in the first figure shows the length of the slit 2.

In the first and second figures, all the slits 2 are arranged in the left-right direction of the figure (hereinafter, also referred to as the X direction). In the first drawing, the slits 2 are arranged in a staggered manner, and in the second drawing, the slits 2 are arranged in a lattice shape.

In Fig. 3, the slit 2 in the X direction and the slit 3 in the Y direction (the direction perpendicular to X) are alternately arranged in either of the X direction and the Y direction.

In the fourth drawing, the two X-direction slits 2, 2 and the two Y-direction slits 3, 3 are grouped together, and one of the X-direction groups and the Y-direction group are alternately arranged in the X direction and the Y direction. In the fourth figure, two slits are used as a group, however, three or more slits may be used as one group.

The arrangement of the slits shown in Figs. 1 to 4 is an example, and the present invention may be arranged in a slit other than the illustration.

When the air diffusing method of the present invention, for the air diffuser, in the area of ventilation unit membrane (the amount of ventilation per 1m ² film) was changed 15Nm ³ / m ² / hr or more to be ventilated, to 15 ~ 40Nm ³ / m ² /hr is better. Thereby, the air diffusing device generates fine bubbles, and the increase in pressure loss is suppressed.

[Examples]

[Examples 1 to 3, Comparative Examples 1 to 5]

For a cylindrical tube substrate having a diameter of 90 mm and a length of 760 mm, an elastic film (film area: 0.18 m ² , thickness: 0.8 mm, material polyurethane) having the composition shown in Table 1 shown in Fig. 1 was attached. Air diffuser. Each air diffusing device was immersed in a water tank filled with clean water (slot capacity: 1.6 m ³ (1 m × 0.4 m × depth 4 m)). Next, in addition to Comparative Example 4, the ventilation amount was 6 Nm ³ /hr (33 Nm ³ /m ² /hr), and only Comparative Example 4 was ventilated with air at a ventilation amount of 2 Nm ³ /hr (11 Nm ³ /m ² /hr). , measure the pressure loss.

The oxygen mobility (calculated as kLa), the pressure loss, the oxygen dissolution power efficiency obtained by the above, and the oxygen movement amount are shown in Table 1.

As shown in Table 1, in the examples 1 to 3, the oxygen dissolution power efficiency and the oxygen movement amount were 1.5 times or more as compared with the conventionally used comparative example 1.

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

In the case of Comparative Example 4 in which the amount of ventilation was small, the power efficiency was higher than that of Examples 1 to 3. However, the amount of oxygen movement 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, if the dissolution efficiency in the sludge is lowered, the oxygen supply is insufficient, and the number of the diffuser must be increased.

In Comparative Example 5 in which the number of slits was 800,000/m ² , the pressure loss was lowered, but the oxygen mobility was lowered, and the increase in the amount of oxygen movement was maintained at 1.3 times that of Comparative Example 1. Further, when observing the bubble generation mode from the air diffusing device, it was confirmed that the gap was too dense, and the generated bubbles were combined with the film surface to be coarsened.

The present invention has been described in detail with reference to the preferred embodiments thereof. However, various modifications may be made by those skilled in the art without departing from the spirit and scope of the invention.

This patent application is based on Japanese Patent Application No. 2012-257569, filed on Nov. 26, 2012, which is hereby incorporated by reference in its entirety.

2‧‧‧ gap

Claims (3)

A method for diffusing air is a tubular membrane type air diffusing device having a tube substrate and an elastic film formed on the tube substrate and forming a plurality of slits for generating fine bubbles, and the ventilation amount per unit membrane area is 15 Nm ³ a method of diffusing air for ventilation of /m ² /hr or more, characterized in that the elastic film is composed of a polyurethane having a thickness of 0.5 to 1 mm, and the slit is arranged in a staggered shape with a length of 0.5. Below mm, there are 200,000 to 600,000 sheets per 1 m ^{2 of} film surface. The method of diffusing gas according to claim 1, wherein the length of the slit is 0.3 to 0.5 mm. The method of dispersing a gas according to claim 1 or 2, wherein the unit membrane area ventilation amount is set to 15 to 40 Nm ³ /m ² /hr.