WO2022005063A1 - Membrane for air diffuser including two kinds of rubber - Google Patents

Abstract

A membrane for an air diffuser according to the present invention has a multi-layered or single-layered structure including two rubber layers of different hardness, and thus can generate air microbubbles having a size of no greater than 1 mm, has an excellent oxygen transfer efficiency with which oxygen in the air is dissolved in wastewater, and improves the durability of a slit to prevent portions that are subjected to high air pressure from easily tearing, thus having the effect of delaying product replacement. In addition, punching of extremely tiny air holes is possible such that permanent compression set, which is a flaw of EPDM-based membranes, is significantly mitigated when the inflow of air is halted, and thus the membrane has the effect of preventing the backflow of wastewater into the membrane air diffuser.

Description

Membrane for diffusers containing two types of rubber

The present invention relates to a membrane for an air diffuser comprising two types of rubber, and more particularly, an acid capable of improving durability and generating microbubbles by manufacturing a multi-layer or single-layer membrane using two types of rubber layers having different shore hardnesses. It relates to tracheal membranes. In addition, it relates to a membrane for a diffuser pipe having improved antifouling properties by forming a diamond-shaped pattern on the surface of the membrane.

The air diffuser is a device to purify water by spraying air, oxygen, and ozone into the water, and the sprayed gas is dissolved in water to provide an environment for oxidation of organic matter, nitrification and growth of microorganisms.

In general, various types of diffusers used in sewage and wastewater treatment facilities are known, and among them, a membrane-type diffuser with micropores perforated in a soft membrane is widely used because of its high oxygen supply rate.

The membrane-type diffuser has a structure in which perforated micropores are opened while the elastic membrane is expanded by compressed air and oxygen is injected, and the air introduced from the blower is finely jetted through the membrane. Since the performance of the diffuser is determined by the oxygen transfer efficiency, it is most important to maximize the oxygen transfer efficiency.

The membrane diffuser generally uses a disk type diffuser, a tube type diffuser, or a plate type membrane diffuser, and a plurality of pores are punched into a membrane made of synthetic rubber or similar thin film.

Examples of such a membrane diffuser are disclosed in Republic of Korea Utility Model Publication Nos. 20-0396008, 20-0232223, and the like.

1 shows the structure of a typical prior art membrane diffuser. In a typical membrane diffuser, a membrane 110 made of a flexible synthetic rubber is laminated and assembled on a diffuser base 120 and then the membrane 110 and the base 120 are fixed by using a fixing nut 160 to fix it. . A screw thread 150 is formed on the side portion of the base 120 for fastening with the fixing nut 160 . A plurality of micropores (slits) for air permeation are perforated in the membrane 110 . In addition, an air orifice 140 for supplying air to the air diffuser is provided at the center of the rear portion of the base 120, and the outer lower end of the air orifice 140 is for a pipe so that the air diffuser can be assembled and installed in the air supply pipe. A screw 130 is formed.

When the air supplied from the air blower is introduced through the air orifice 140 , the flexible membrane 110 expands by the pressure of the air, and the slit formed in the membrane is opened. At this time, air may be introduced into the aeration tank through the opened slit.

In addition, when the compressed air supplied from the air blower is stopped, the membrane 110 is seated on the diffuser base 120, the expanded slit is closed, and at the same time the slit is not punched in a certain area in the center of the membrane 110 It is seated on the air orifice 140 and is manufactured to block the treated water from flowing back into the air supply pipe.

Air supplied from the air blower ejects air bubbles having a diameter of less than 5 mm into the treated water through a plurality of slits formed in the membrane 110 .

In addition, the flow of the treated water is formed on the surface of the aeration tank by air bubbles ejected from the treated water, thereby preventing solids from accumulating on the bottom of the aeration tank.

As a synthetic rubber material, ethylene propylene monomer (EPDM), silicone, acrylonitrile-butadiene rubber (NBR), fluoroelastomer (FKM), etc. are used for the elastic membrane.

In addition, the surface of the membrane is coated with PTFE (Polytetrafluoroethylene) or treated with fluorine to reduce the adhesion of foreign substances in the water, and the physical properties of the membrane can be maintained for a long time.

However, since these membrane diffusers use air pressure, they are excessively expanded and ruptured or lose elasticity according to changes in air pressure. It is important to provide a diffuser capable of delivering good and uniform oxygen.

Furthermore, in order to increase the oxygen transfer efficiency, it is important to reduce the size of air bubbles ejected from the membrane. If the size of the slit is formed small to reduce the size of air bubbles, the membrane is stretched too much, and the durability of the PTFE coated on the surface is quickly reduced. There was a problem with damage.

SUMMARY OF THE INVENTION It is an object of the present invention to provide a membrane for a diffuser pipe that is capable of generating fine-sized bubbles and has greatly improved durability.

In order to achieve the above object, the present invention provides a first rubber layer having a Shore A hardness of 50 to 70; and a second rubber layer laminated on the first rubber layer and having a Shore A hardness of 60 to 75.

In the present invention, the first rubber layer and the second rubber layer are each independently selected from the group consisting of EPDM (Ethylene Propylene Monomer), silicone, NBR (acrylonitrile-butadiene rubber) and FKM (Fluoroelastomer). can be configured.

In the present invention, the ratio of the thickness of the first rubber layer and the second rubber layer is preferably 1:1 to 3:1.

The membrane for a diffuser of the present invention may be characterized in the form of a tube.

In the membrane for a diffuser of the present invention, a plurality of intaglio or embossed patterns may be formed on the surface of the uppermost layer of the membrane.

The present invention also provides a second rubber layer having a Shore A hardness of 60 to 75; and a first rubber layer formed on the outside of the second rubber layer and having a Shore A hardness of 50 to 70.

In the present invention, the diameter of the second rubber layer is preferably 1/4 to 1/2 of the diameter of the entire membrane.

Oxygen transfer efficiency ( Oxygen Transfer Efficiency) is excellent, and the durability of the slit is improved to prevent easy tearing of parts subjected to large air pressure, thereby delaying product replacement time. In addition, it is possible to perforate extremely fine air holes, so that when air inflow is stopped, the permanent compression set, which is a disadvantage of the EPDM-based membrane, is greatly improved, thereby preventing the reverse flow of wastewater into the membrane diffuser.

1 shows the structure of a typical prior art membrane diffuser.

2 is a cross-sectional view of a membrane for a diffuser according to an embodiment of the present invention.

3 is a cross-sectional view of a membrane for a diffuser including a PTFE layer according to an embodiment of the present invention.

4 is a cross-sectional view of a membrane for a diffuser according to another embodiment of the present invention.

5 shows a cross-sectional view of a membrane for a diffuser including a PTFE layer according to another embodiment of the present invention.

6 shows a membrane for a diffuser having a diamond-shaped pattern formed on its surface, according to an exemplary embodiment of the present invention.

7 is a photograph comparing the generation of bubbles according to air supply by putting the diffuser according to an embodiment of the present invention into a water tank. In FIG. 7, (a) is a diffusion pipe using a conventional single-layer membrane, (b) is a diffusion pipe in which a diamond pattern is formed on the surface of the single-layer membrane, (c) is a first layer of Shore A hardness of 60 and Shore A hardness The diffuser of the present invention in which the second layer of 70 is composed of multiple layers, and (d) shows the diffuser of the present invention in which the first layer of Shore A hardness of 60 and the second layer of Shore A hardness of 70 are constituted as inner and outer layers.

Unless defined otherwise, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art to which this invention belongs. In general, the nomenclature used herein is those well known and commonly used in the art.

The present invention relates to a membrane for an aeration pipe installed in an aeration tank of a wastewater treatment plant to efficiently dissolve oxygen in the air into wastewater by dispersing it in treated water by forming ultra-fine bubbles of air supplied from a blower.

As shown in FIG. 2 , the membrane for a diffuser according to the present invention is made of rubber having different shore A hardness in multiple layers, but by laminating a rubber having a higher shore A hardness as an upper layer, through a slit As the size of the ejected bubble was reduced, the oxygen transfer efficiency was increased and the durability was greatly improved.

Specifically, the membrane for a diffuser of the present invention includes a first rubber layer 10 having a Shore A hardness of 50 to 70 and a second rubber layer laminated on the first rubber layer 10 and having a Shore A hardness of 60 to 75 ( 20) is included.

The first rubber layer 10 and the second rubber layer 20 may use a synthetic rubber generally used for a membrane for an air diffuser, for example, EPDM (Ethylene Propylene Monomer), silicone, NBR (acrylonitrile-butadiene rubber) , FKM (Fluoroelastomer), etc. can be used.

The first rubber layer 10 and the second rubber layer 20 are preferably made of the same rubber material. Since the first and second rubber layers 10 and 20 are made of the same material, the two rubber layers can be firmly fixed by pressing without forming an adhesive layer or a primer layer between the rubber layers.

In a preferred embodiment of the present invention, EPDM may be used as a material for the first rubber layer 10 and the second rubber layer 20 .

In the present invention, the first rubber layer 10 preferably has a Shore A hardness of 50 to 70, more preferably a Shore A hardness of 55 to 65, and most preferably a Shore A hardness of 58 to 62. In general, considering that the hardness used for the membrane for the diffuser is about 60, the first rubber layer 10 may use a rubber having the hardness generally used for the membrane for the diffuser.

In addition, the thickness of the first rubber layer 10 is preferably 1 to 2 mm, more preferably 1.3 to 1.7 mm.

In the present invention, the second rubber layer 20 preferably has a Shore A hardness of 60 to 75, more preferably a Shore A hardness of 65 to 75, and most preferably a Shore A hardness of 68 to 72. By controlling the Shore A hardness of the second rubber layer 20 in this way, it is possible to withstand a greater tensile force acting on the outside than on the inside of the membrane, so that the degree of slit widening is similar to that of the first rubber layer 10 and is stably 1 mm or less. of air bubbles can be ejected, and the durability is long lasting.

The thickness of the second rubber layer 20 is preferably 0.7 to 1.3 mm, more preferably 0.9 to 1.1 mm.

That is, it is preferable to configure the thickness ratio of the first rubber layer 10 and the second rubber layer 20 to be 1:1 to 3:1, and a thickness ratio of 1.3:1 to 1.7:1 is preferable.

The surface of the second rubber layer 20 may be coated with PTFE or treated with fluorine. As described above, through the surface treatment of the membrane, the adhesion of foreign substances in the water is reduced, and the physical properties of the membrane can be maintained for a long time by acting as a protective film for the membrane made of synthetic rubber against water.

As illustrated in FIG. 3 , the PTFE coating layer 30 may be coated with a PTFE layer by a known technique after forming a primer layer 40 on the second rubber layer 20 according to a known technique.

By perforating a plurality of fine pores of less than 1 mm in the membrane for a diffuser having a multilayer structure of the present invention, air bubbles of less than 1 mm can be ejected into the wastewater. Through this, compared to the existing air diffuser, the oxygen transfer efficiency of dissolving oxygen in the air supplied from the blower into the wastewater can be greatly improved, and at the same time, it is possible to significantly improve the compression set, which is a disadvantage of EPDM when it is not in operation, and thus prevent clogging of pores. can be prevented

The perforation is preferably configured in a slit shape, so that the slit opens when the membrane is expanded by air pressure and closes when no air is injected.

When the slit is simply formed to be small in order to evenly eject air bubbles having an average diameter of 1 mm or less in the membrane for a diffuser of the prior art, the air pressure increases and the membrane over-expands, shortening the service life, and the outer slit is partially opened. As a result, there was a problem that the air bubbles could not be ejected uniformly.

The multilayer membrane of the present invention has different hardnesses of the first layer and the second layer, so that when the membrane is expanded by air injection, it expands well enough in the direction in which air is introduced to ensure that the slit of 1 mm is well opened Conversely, the wastewater-side rubber attenuates the elongation to suppress excessive expansion of the membrane, thereby increasing the durability of the membrane while maintaining the size of air bubbles ejected through the slit within 1 mm. Therefore, compared to a membrane having a general structure, the replacement time can be delayed by increasing the durability of the membrane while increasing the oxygen transfer efficiency for dissolving oxygen in the air in the wastewater.

In an exemplary embodiment of the present invention, the membrane for the diffuser may be manufactured in the form of a tube.

When the membrane is manufactured in the form of a tube, the inner side of the tube may be formed as the first rubber layer, and the outer side may be formed as the second rubber layer.

In another embodiment of the present invention, as shown in FIG. 4 , the membrane for a diffuser of the present invention may be configured to include a first rubber layer 10 on the outside and a second rubber layer 20 on the inside.

In the present invention, the "outer" and "inner" are mainly circular membranes (disk-shaped or plate-shaped). A small circle including the center is referred to as an inner side, and the remaining donut-shaped portion formed outside the inner small circle is expressed as an outer side.

The inner side of the membrane is composed of a second rubber layer 20 having a Shore A hardness of 60 to 75, and the outer side of the membrane is composed of a first rubber layer 10 having a Shore A hardness of 50 to 70. By more robustly protecting the center directly exposed to the input air pressure, pores of 1 mm or less can be ejected uniformly over the entire membrane, and the problem of rapid aging of the center and quick replacement can be solved.

In addition, by manufacturing the Shore A hardness of the inner and outer parts of the disc differently, the air pressure introduced from the blower catches the expansion at the inner center, and the air moves to the outer side, generating fine bubbles in the entire disc part even with a small input pressure. This can greatly increase the oxygen transfer efficiency.

The diameter of the inner second rubber layer 20 is preferably 1/4 to 1/2 of the diameter of the entire membrane.

Since the first rubber layer 10 and the second rubber layer 20 are made of the same material, it is possible to firmly bond them by pressing without forming an adhesive layer or a primer layer.

When the membrane for the diffuser is configured as a single layer as described above, the thickness of the first and second rubber layers is preferably 2.1 to 2.5 mm.

In addition, as shown in FIG. 5 , it is also possible to form a primer layer 40 on the surface of the membrane for a diffuser of the present invention including the first and second rubber layers on the inside and outside, and then coat the PTFE coating layer 30 . .

In a preferred embodiment of the present invention, for example, a diamond-shaped pattern may be formed on the surface of the uppermost layer of the membrane for the diffuser.

By forming a pattern on the surface of the membrane, contaminants can be easily removed without adhering to the surface of the membrane.

The pattern is preferably, as shown in FIG. 6 , inverted-polygonal cone-shaped engraved patterns such as diamonds may be formed on the surface of the membrane to a depth of 0.05 to 0.2 mm.

The pattern may form an intaglio or embossed pattern by eroding the surface of the rubber membrane in the shape of a predetermined pattern.

Alternatively, the pattern may form an intaglio or embossed pattern by forming an additional coating layer such as a nonwoven fabric on the uppermost layer of the membrane and etching the additional coating layer.

Example

Hereinafter, the present invention will be described in more detail through examples. These examples are only for illustrating the present invention, and it will be apparent to those of ordinary skill in the art that the scope of the present invention is not to be construed as being limited by these examples.

Experimental Example 1: Cell size and durability test according to the type of diffuser membrane

As shown in FIG. 1, an experiment was performed by changing the type of membrane in a conventional air diffuser.

Using a commonly used EPDM single-layer membrane having a shore hardness of 60, the size of the bubble generation was measured under a condition of 2 bar air pressure, and it is shown in Table 1 below.

In addition, the cell size was measured using a multilayer membrane in which a first rubber layer having a shore hardness of 60 and a second rubber layer having a shore hardness of 70 were laminated and a multilayer membrane in which a second rubber layer having a shore hardness of 80 was laminated, respectively, and described in the table below. .

division	Shore A hardness	Air pressure (bar)	Bubble size (mm)
Comparative Example 1	60	2	1 to 2
Example 1	Bottom: 60 Awards: 70	2	0.5 to 1.2
Comparative Example 2	Bottom: 60 Award: 60	2	Unusable due to increased air pressure

As can be seen from the above table, in the case of the multi-layered membrane according to the embodiment, it can be seen that the size of the bubbles is reduced compared to the conventional single-layered membrane.

In particular, in the case of the diffuser of Example 1, it can be seen that the bubble size is very small, 0.5 to 1.2 mm, and uniform bubbles are generated without clogging the slit. This is because, due to the double rubber layer structure, the slit can be sufficiently expanded in the first layer, and the membrane is well contained in the second layer from excessive swelling. Therefore, it can be expected that the membrane of Example 1 has significantly superior durability compared to the membrane of Comparative Example 1, which is greatly inflated to generate 1 to 2 mm of air bubbles.

On the other hand, when the shore hardness of the upper layer of the multilayer membrane was set to 80, no bubbles were generated at an air pressure of 2 bar, so the experiment was impossible.

Experimental Example 2: Water bath bubble generation experiment (1)

In order to visually compare and confirm the size of the generated air bubbles, a comparison result is shown in FIG. 7 by introducing an air diffuser into the water tank to generate air.

In FIG. 7, (a) is a diffusion pipe using a conventional single-layer membrane, (b) is a diffusion pipe in which a diamond pattern is formed on the surface of the single-layer membrane, (c) is a first layer of Shore A hardness of 60 and Shore A hardness of 70 The diffuser pipe of the present invention composed of a second layer of multilayer, and (d) shows the diffuser pipe of the present invention composed of a first layer having a shore A hardness of 60 and a second layer having a shore A hardness of 70 as inner and outer layers.

As can be visually compared in FIG. 7 , in the case of a diffuser using a conventional single-layer membrane, the bubble size was irregular and most exhibited a size of 1 mm or more.

However, it can be seen that in the case of the diffusers of (c) and (d) using the first and second rubber layers of the present invention, it is possible to eject uniformly and very small-sized air bubbles.

In addition, in the case of the diffuser tube (b) in which a diamond-shaped pattern was formed on a single layer, the bubble size did not become small, but it was confirmed that there was no contaminant on the surface, so that foreign matter was not clogged in the slit, so that bubbles of a uniform size could be generated. .

Experimental Example 3: Water bath bubble generation experiment (2)

In the above experimental example, air bubbles were formed using the diffuser pipe (d) of the present invention, which consisted of a diffuser pipe (a) using a conventional single-layer membrane, a first layer having a shore A hardness of 60, and a second layer having a shore A hardness of 70, as inner and outer layers. incidence was compared.

The time until 100% microbubbles were generated and the size of the generated air bubbles were measured and shown in the table below by inputting a pressure of 3 bar at a depth of 1 m with a 300 mm diameter diffuser.

division		Primary	Secondary	tertiary
single layer membrane diffuse organ (a)	Outer bubble generation time	15 seconds	16 seconds	16 seconds
	bubble size	2.5mm	2.5mm	2.5mm
Hardness inside and outside different diffuse organs (d)	Outer bubble generation time	10 seconds	9 seconds	11 seconds
	bubble size	1.5mm	1.5mm	1.5mm

In the above table, in the conventional single hardness membrane diffuser (a), it took about 15 seconds or more to generate 100% microbubbles on the outside, and the size of the bubbles was also large as 2.5mm, but the internal and external hardness of the present invention was The different diffuser tubes (d) take a very fast time of about 10 seconds to generate 100% air bubbles on the outer side, and the size of the air bubbles is also confirmed to be small and uniform about 1.5 mm.

As described above in detail a specific part of the content of the present invention, for those of ordinary skill in the art, this specific description is only a preferred embodiment, and the scope of the present invention is not limited thereby It will be obvious. Accordingly, it is intended that the substantial scope of the present invention be defined by the appended claims and their equivalents.

Claims (7)

1. a first rubber layer having a Shore A hardness of 50 to 70; and

   A second rubber layer laminated on the first rubber layer and having a Shore A hardness of 60 to 75

   including,

   wherein the Shore A hardness of the second rubber layer is higher than the Shore A hardness of the first rubber layer.
2. The method of claim 1,

   The first rubber layer and the second rubber layer are each independently selected from the group consisting of EPDM (Ethylene Propylene Monomer), silicone, NBR (acrylonitrile-butadiene rubber) and FKM (Fluoroelastomer), characterized in that it is composed of one rubber , membranes for diffusers.
3. The method of claim 1,

   The thickness ratio of the first rubber layer and the second rubber layer is 1:1 to 3:1, characterized in that the membrane for a diffuser pipe.
4. The method of claim 1,

   A membrane for a diffuser, characterized in that the membrane is in the form of a tube.
5. The method of claim 1,

   A membrane for diffusers, characterized in that a plurality of intaglio or embossed patterns are formed on the surface of the uppermost layer of the membrane.
6. a second rubber layer having a Shore A hardness of 60 to 75; and

   A first rubber layer formed on the outside of the second rubber layer and having a Shore A hardness of 50 to 70

   including,

   wherein the Shore A hardness of the second rubber layer is higher than the Shore A hardness of the first rubber layer.
7. 7. The method of claim 6,

   A membrane for a diffuser pipe, characterized in that the diameter of the second rubber layer is 1/4 to 1/2 of the diameter of the entire membrane.

Images