Patent Application
20070095937
1. Field of the Invention
The present invention relates to a system and a method for generating a microbubble-contained liquid, and a microbubble generator to be assembled in the system
2. Background Art
Recently, a gas-supersaturated liquid containing microbubbles has been attracting attention as being a liquid usable widely in the fields of precision-machine cleaning, agriculture, oil separation, water purification, hot spring, etc. Existing systems for generating a microbubble-contained liquid use filters. Such filter-type microbubble-contained liquid generating systems are liable to fall in filter clogging, and they cannot keep their initial performance for a long term.
U.S. Pat. No. 6,293,529 discloses an apparatus for generating microbubbles. This apparatus includes a cylinder having a bulkhead with liquid holes at the upstream end thereof and a disk disposed opposite to the bulkhead, such that the bulkhead and the disk define a restriction passage. Thereby, a gas-dissolved liquid (a liquid containing dissolved gas) is forced to pass through the restriction passage to generate a large quantity of microbubbles in the liquid.
It is known that microbubbles had better be smaller and smaller in diameter to (1) absorb suspended solids (solids suspended in water) more effectively, (2) increase the contact area between water and air and elongate the duration of time where the bubbles drift densely in water to contribute to more efficient decomposition of organic matter, and (3) penetrate more deeply into objects to be cleaned and thereby enhance the cleaning effect.
In the apparatus disclosed in U.S. Pat. No. 6,293,529, however, the microbubbles contained in the gas-supersaturated liquid are relatively large in diameter. So, the microbubble-contained liquid generated by the apparatus is applicable only to a limited field of industry.
It is therefore desirable to overcome the above-mentioned drawbacks of the existing techniques by providing a system and a method for generating a microbubble-contained liquid, capable of generating a liquid containing bubbles smaller in diameter than ever, as well as a microbubble generator to be assembled in the system.
It is also desirable to provide a system and a method for generating a microbubble-contained liquid, capable of generating a liquid in which microbubbles remain stably for a long time, as well as a microbubble generator to be assembled in the system.
It is also desirable to provide a system and a method for generating a microbubble-contained liquid, capable of generating a liquid that contains microbubbles less variable in diameter from one another, as well as a microbubble generator to be assembled in the system.
According to an aspect of the present invention, one or more of those objects of the invention are accomplished by providing a method of generating a microbubble-contained liquid that is a liquid containing microbubbles, comprising: preparing a restriction passage having a recess formed in a wall surface thereof; and forwarding a gas-dissolved liquid under pressure with a pump and making the gas-dissolved liquid pass through the restriction passage to generate a large quantity of microbubbles in the liquid.
In the first aspect of the invention, the gas-dissolved liquid is made to pass through the restriction passage to generate microbubbles by cavitation. When the gas-dissolved liquid passes through the restriction passage, a whirling flow occurs in the recess formed in the wall surface of the restriction passage. In this process, very small bubbles are produced. The whirling occurring at the recess contributes to reducing diameters of the bubbles and/or uniforming diameters of the bubbles. Microbubbles reduced in diameter can continue to exist in the microbubble-contained liquid for a long period of time. Also, since no filter is used for generation of microbubbles, the microbubble-contained liquid generating system can be easily maintained in a proper condition.
According to the second aspect of the invention, there is provided a method of generating a microbubble-contained liquid that is a gas containing microbubbles, comprising: a step of mixing a gas into a liquid supplied from a liquid source to prepare a gas-dissolved liquid; a step of drawing and forwarding the gas-dissolved liquid under pressure with a pump; and a step of making the gas-dissolved liquid forwarded under pressure by the pump to pass through a restriction passage having a recess formed in a wall surface thereof, and thereby generating a large quantity of microbubbles.
In the second aspect of the invention, a liquid containing a large quantity of microbubbles can be generated by making the gas-dissolved liquid forwarded under pressure from the pump to pass through the restriction passage having the recess formed in the wall surface thereof. To further reduce the sizes of the microbubbles, the microbubble-contained liquid exiting from the restriction passage is preferably driven to hit against a stationary surface.
According to a preferred embodiment of the invention, there is provided a microbubble generator, comprising: a main pipe through which a gas-dissolved liquid supplied under pressure flows; an intermediate wall partitioning the main pipe and having openings formed in a central portion thereof; a small-diameter pipe continuous from a downstream wall surface of the intermediate wall to face to the openings; a flange provided at the downstream end of the small-diameter pipe to extend radially outward; and a disk disposed to close the downstream end of the small-diameter pipe, wherein the disk and flange in combination define a restriction passage, and a recess is formed in one or both of opposed surfaces of the disk and the flange.
By changing the distance between the flange and the disk which define the restriction passage together, it is possible to control the diameters of the microbubbles generated by the microbubble generator. As the disk is brought nearer to the flange, the bubbles tend to decrease in size. On the contrary, as the disk is moved more distant from the flange, the bubbles tend to increase in size.
The foregoing and other features, aspects and advantages of the present invention will be come apparent from the following detailed description of the embodiments of the present invention when taken in conjunction with the accompanying drawings.
The circulation pump 2 is connected at an outlet thereof to the bottom of the pressure tank 3 via a forced feeding pipe 6. Ann upstream end of a circulation pipe 7 is connected to the lower portion of the pressure tank 3. A down stream end of the circulation pipe 7 is connected to a middle portion of the raw water pipe 5. The circulation pipe 7 has a venturi tube 8 (
Referring to
The circulation pipe 7 preferably has a first flow control valve 12 located upstream of the venturi tube 8 and a second flow control valve 13 located downstream of the venturi tube 8. Thus, the first flow control valve 12 can substantially control the pressure in the pressure tank 3, and the second flow control valve 13 can substantially control the air intake through the suction port 9. Preferably, the first and second flow control valves 12 and 13 are of a manually controllable type such that an operator of the microbubble-contained liquid generating system can manually adjust the pressure in the pressure tank 3 by monitoring the pressure gage PG.
On the top of the pressure tank 3, a relief valve 15 is provided to discharge excessive air from the pressure tank 3. Through the relief valve 15, internal air is discharged from the pressure tank 3 to keep it approximately full of water. Also, an upstream end of a discharge pipe 16 is connected to the pressure tank 3 preferably at a level higher than the circulation pipe 7. The discharge pipe 16 has a microbubble generator 20 at an upstream portion thereof. A microbubble-contained liquid generated in the microbubble generator 20 is discharged into the water bath 4.
Referring to
The inner cylinder 203 is coaxial with the outer cylinder 201. The inner cylinder 203 has a ring-shaped circumferential flange 203a formed to extend radially from the downstream end thereof. More specifically, the circumferential flange 203a extends in a direction perpendicular to the downstream end of the inner cylinder 203, and the circumferential perimeter of the circumferential flange 203a is adjacent to the inner wall of the outer cylinder 201.
The microbubble generator 20 includes a disk 204 located adjacent to the rear perimeter of the inner cylinder 203 and extending across the outer cylinder 201. The disk 204 defines a restriction passage 17 in combination with the circumferential flange 203a. The disk 204 preferably has a step 204a formed by removing an amount of the downstream surface portion from a circumferential perimeter portion of the disk 204. The disk 204 is mounted on a support pin 205 extending downstream from a central portion of the bulkhead 202 along its axial line. In this embodiment, the disk 204 is fixed by welding after adjustment of the distance between the disk 204 and the circumferential flange 203a. However, the disk 204 may be movable relative to the support pin 205 to allow adjustment of the distance between the circumferential flange 203a and the disk 204 can be adjusted.
A recess 206 is formed between the circumferential flange 203a forming the wall surface of the restriction passage 17 and a portion of the disk 204 opposed to the circumferential flange 203a to indent into at least one of these opposed surfaces. In this embodiment, the recess 206 is formed to indent into the circumferential flange 203a as shown in
Water in the water bath 4 is introduced into the microbubble-contained liquid generator 1 by the circulation pump 2, and forwarded under pressure to the pressure tank 3. The water is thus contained in the pressure tank 3 under pressure. The water in the pressure tank 3 is partially returned to the water bath 4 via the discharge pipe 16 and the microbubble generator 20, and partially flows into the circulation pipe 7. The water having flowed into the circulation pipe 7 takes in air from the suction port 9 while it passes through the venturi tube 8. Then, the water containing the air merges the raw water coming from the raw water pipe 5, and it is pumped up by the circulation pump 2. The air in the water is crushed into relatively small bubbles by the circulation pump 2, and dissolution of air into the water is promoted.
In a predetermined length of time after the microbubble-contained liquid system 1 is driven, the water in the pressure tank 3 becomes air-dissolved water containing and mixed with bubbles, and fills the pressure tank 3. After the system 1 stably exhibits this condition, until the water is discharged from the pressure tank 3 into the water bath 4 via the discharge pipe 16, the water passes through the restriction passage 17 of the microbubble generator 20, and the water exiting from the restriction passage 17 is discharged to the water bath 4 via the outer cylinder 201 while hitting against the inner wall of the outer cylinder 201.
The microbubble generator 20 further includes a pressure chamber 210 defined by the bulkhead 202 and the inner cylinder 203, and the restriction passage 17 communicates with this pressure chamber 210. More specifically, the inner cylinder 203 serves as a side wall of the pressure chamber 210, and the pressure chamber 210 has a depth corresponding to the lengthwise size of the inner cylinder 203. The deep portion of the pressure chamber 210 communicates with the restriction passage 17. The microbubble generator 20 further includes a low-pressure chamber 211 defined by a downstream portion of the outer cylinder 201. An auxiliary chamber 212 communicating with the low-pressure chamber 211 is preferably provided between the outer cylinder 201 and the inner cylinders 203.
The air-dissolved water containing and mixed with bubbles, which flows from the pressure tank 3 and reaches the discharge pipe 16, then enters into the pressure chamber 210 via the liquid passage holes 202a formed in the bulkhead 202 of the microbubble generator 20. Then, it goes out from the pressure chamber 210 and passes through the clearance between the circumferential flange 203a of the inner cylinder 203 and the disk 204, namely, through the restriction passage 17. Further, the air-dissolved water is spurted from the restriction passage 17, and enters into the low-pressure chamber 211 of the outer cylinder 201 while hitting against the inner wall of the outer cylinder 201 and bringing the phenomenon of cavitation.
The air-dissolved water in the pressure tank 3 creates a whirl flow in the recess 206 in the wall surface of the restriction passage 17 when passing through the restriction passage 17. The whirl flow causes generation of microbubbles in the water. Then, just after exiting from the restriction passage 17, the microbubbles strike the inner wall of the outer cylinder 201 and become miniaturized more.
Experimental tests proved that the amount of oxygen dissolved in the water bath 4 changed with time as follows:
Conditions of the tests were as follows:
(1) Capacity of the water bath 4 300 liters
(2) Circulation pump 2 1.5-kW motor
(3) Flow rate of air through the suction port 9 1.5 liters/min
Diameters and numbers (in 1 ml of water) of bubbles contained in the microbubble-contained water generated by the microbubble-contained liquid generating system 1 were proved to be as follows:
For improvement of the water quality, it is known that diameters of bubbles are preferably about 5 to 50 μm to attain a buoyancy capable of raising suspended solids to the water surface. Also, as already known, bubbles having diameters larger than 10 μm tend to join together into larger bubbles, each other and tend to there is a tendency that in diameter will easily join each other to result in larger bubbles, and as the diameters get smaller and smaller than 10 μm, bubbles tend repel each other and become difficult to join together.
It will be understood from the result of the tests that the distribution of diameters of the microbubbles generated by the microbubble-contained liquid generating system 1 have peaks at 20 μm and between 0.1 to 0.05 μm. Of course, diameters of microbubbles generated by the system can be changed by adjusting the distance between the circumferential flange 203a and the disk 204 and/or by regulating the pressure in the pressure tank 3. However, it should be remarked that the microbubble-diameter distribution has peaks. This means that variety in diameter of bubbles contained in the microbubble-contained water is small.
The microbubble-contained water produced by the tests and containing bubbles with diameters having peaks at peaks at 20 μm and between 0.1 to 0.05 μm has both the function of raising suspended solids up to the water surface and the function of retaining a large quantity of microbubbles in the water. The latter function meets the fact that the high concentration of dissolved oxygen was maintained even after expiration of 24 hours from interruption of operation of the microbubble-contained liquid generating system 1. It will be understood from the result of the tests that, although diameters of bubbles generated by existing microbubble-contained liquid generating apparatuses were several μm, the microbubble-contained liquid generating system 1 according to the embodiment of the invention can generate bubbles having diameters reduced to one tenth or less. Therefore, microbubbles contained in the microbubble-contained water generated by the system 1 according to the embodiment of the invention continue to exist for a long period of time.
The microbubble-contained liquid generating system 1 may be modified to use an air nozzle, for example, in place of the venturi tube 8. That is, with the nozzle end being disposed in the circulation pipe 7 (as shown in
With reference to
Heretofore, some preferred embodiments of the present invention have been explained in conjunction with the drawings. The present invention, however, contemplates the following changes and modifications.
As the first modification, the restriction passage 17 included in the microbubble generator 20 or any one of its modifications may be a thin tube, and the inner wall of the outer cylinder 201 may be replaced by a stationary, fixed, collision surface for collision of microbubble-contained liquid spurting from the restriction passage 17.
As the second modification, the pressure chamber 210 provided in the microbubble generator 20 or any one of its modifications may be omitted by instead increasing the pressure in the pressure tank 3. In other words, if the pressure chamber 210 is provided in the microbubble generator 20, for example, then the pressure in the pressure tank 3 can be reduced to a relatively low level. As a result, a relatively small pump may be used as the circulation pump 2, and the cost of the microbubble-contained liquid generating system 1 can be reduced accordingly.
As the third modification, if the pressure chamber 210 is provided in the microbubble generator 20 or any one of its modifications to supply a gas-dissolved liquid under a relatively high pressure to the restriction passage 17, then the bubbles contained in the microbubble-contained liquid from the restriction passage 17 can be increased in number or further reduced in size. Therefore, in the case where the bubbles may have diameters equal to or slightly smaller than those of bubbles generated by existing techniques, the recess 206 may be omitted from the restriction passage 17.
The microbubble-contained liquid generating system according to the present invention can generate a liquid containing microbubbles of any of various gases such as air, carbon dioxide (CO2), nitrogen gas (N2), ozone (O3), chloride gas (Cl2), inactive gas, etc., and the microbubble-contained liquids containing such microbubbles can be used for various purposes. For example, such liquids can be used in home baths and cosmetic baths, as cosmetic liquids, in hot springs and swimming pools, for water purification of rivers and lakes, water treatment in water supply and sewerage systems, for washing and sterilization of farm crops such as vegetables, as oxygen-rich drinking water for livestock, for washing and sterilization of eggs, and filtration in beer manufacturing, as fish-culturing water, medical-use water against skin infection, for treatment of industrial waste liquid, for washing semiconductor chips and precision machines, washing of pipes, treatment of crude-carrier ballast, oil separation, floating and removal of dissolved substances, etc.
| Number | Date | Country | Kind |
|---|---|---|---|
| JP2004-161184 | May 2004 | JP | national |
| Number | Date | Country | |
|---|---|---|---|
| Parent | PCT/JP05/10208 | May 2005 | US |
| Child | 11564573 | Nov 2006 | US |
