Gas and liquid contact apparatus – Contact devices – Rotating gases
Reexamination Certificate
1999-08-30
2002-05-07
Bushey, C. Scott (Department: 1724)
Gas and liquid contact apparatus
Contact devices
Rotating gases
C261S123000
Reexamination Certificate
active
06382601
ABSTRACT:
FIELD OF THE INVENTION
The present invention relates to a micro-bubble generating system for efficiently dissolving gas such as the air, oxygen gas, etc. into liquid such as city water, river water, etc., for purifying polluted water and for effectively utilizing the water for reconditioning and renewal of water environment.
BACKGROUND ART
In conventional type aeration systems, e.g. in most of aeration systems using micro-bubble generating system installed for culture and growth of aquatic animals, air bubbles are generated by injecting the air under pressure into water through fine pores of tubular or planar micro-bubble generating system installed in the tank, or air bubbles are generated by introducing the air into water flow with shearing force or by vaporizing the air dissolved in water by rapidly reducing pressure of the pressurized water.
In the aeration process using the micro-bubble generating system with the above functions, operation is basically controlled by adjusting the air supply quantity or the number of the micro-bubble generating systems to be installed, while it is necessary to efficiently dissolve gas such as air, carbon dioxide, etc. into water and further to promote circulation of the water.
However, in the aeration system using the conventional type micro-bubble generating system, e.g. diffusion system based on injection, even when fine pores are provided, when air bubbles are injected under pressure through pores, volume of each of the air bubbles is expanded, and diameter of each air bubble is increased to several millimeters due to surface tension of the air bubbles during injection. Thus, it is difficult to generate air bubbles of smaller diameter. Also, there are problems such as clogging of the pores or increase of power consumption caused by the operation for long time.
In the system to generate the air bubbles by introducing the air into water flow with shearing force using vanes and air bubble jet stream, it is necessary to have higher number of revolutions to generate cavitation. Also, there are problems of power consumption increase and the problem of corrosion of vanes or vibration caused by generation of cavitation. Further, there are problems in that only a small amount of micro-bubbles can be generated.
In the system where gas-liquid two-phase flow collides with the moving vane or projection, fishes or small aquatic animals in natural lakes or culture tanks may be injured, and this causes trouble in the development and maintenance of the environmental condition necessary for the growth of fishes and other aquatic animals.
Further, in the pressurizing system, the system must be designed in larger size and requires higher cost, and operation cost is also high.
In none of the prior art in this field as described above, it has been possible to generate micro-bubbles with diameter of not more than 20 &mgr;m in industrial scale.
SUMMARY OF THE INVENTION
After fervent study efforts, the present inventors have successfully developed the present invention, by which it is possible to generate micro-bubbles with diameter of not more than 20 &mgr;m in industrial scale.
As shown in
FIG. 12
, which indicates the principle of the system according to the present invention, a micro-bubble generating system is provided, which comprises a conical space
100
in a container, a pressure liquid inlet
500
provided in tangential direction on a part of circumferential surface of inner wall of the space, a gas introducing hole
80
opened at the center of the bottom
300
of the conical space, and a swirling gas-liquid outlet
101
near the top of the conical space.
The entire system or at least the swirling gas-liquid outlet
101
is submerged in the liquid, and by sending pressure liquid from the pressure liquid inlet
500
into the conical space
100
, a swirling flow is formed inside, and negative pressure is generated along the axis of the conical tube. By this negative pressure, the gas is sucked through the gas introducing hole
80
. As the gas passes along the axis of the tube where the pressure is at the lowest, a narrow swirling gas cavity
60
is generated.
In the conical space
100
, a swirling flow is generated from the inlet (pressure liquid inlet)
500
toward the outlet (swirling gas-liquid outlet)
101
. As cross-sectional area of the space
100
is gradually reduced toward the swirling gas-liquid outlet
101
, both the swirling velocity and velocity of the flow directed toward the outlet are increased at the same time.
In association with this swirling, centrifugal force is applied on the liquid and centripetal force is applied on the air at the same time because of the difference of specific gravity between the liquid and the gas. As a result, the liquid portion and the gas portion become separable from each other, and the gas is turned to a narrow thread-like gas swirling cavity
60
, which is narrowed down and runs continuously up to the outlet
101
and is then injected through the outlet. At the same time as the injection, swirling is rapidly weakened by the surrounding stationary water. Then, radical difference in swirling velocity occurs before and after that point. Because of the difference of swirling velocity, the thread-like gas cavity
60
is cut off in continuous and stable manner. As a result, a large amount of micro-bubbles, e.g. micro-bubbles of 10 to 20 &mgr;m in diameter, are generated near the outlet
101
and are discharged.
Specifically, the present invention provides:
(1) a swirling type micro-bubble generating system, comprising a container main unit having a conical space, a pressure liquid inlet provided in tangential direction on a part of circumferential surface on inner wall of the space, a gas introducing hole opened on the bottom of the conical space, and a swirling gas-liquid outlet arranged at the top of the conical space;
(2) a swirling type micro-bubble generating system, comprising a container main unit having a truncated conical space, a pressure liquid inlet provided in tangential direction on a part of circumferential surface on inner wall of the space, a gas introducing hole opened on the bottom of the truncated conical space, and a swirling gas-liquid outlet arranged in the upper portion of the truncated conical space;
(3) a swirling type micro-bubble generating system, comprising a container main unit having a space of bottle-like shape, a pressure liquid inlet provided in tangential direction on a part of circumferential surface on inner wall of the space, a gas introducing hole opened on the bottom of the bottle-like space, and a swirling gas-liquid outlet arranged at the top of the bottle-like space;
(4) a swirling type micro-bubble generating system according to one of (1) to (3) above, wherein a plurality of pressure liquid inlets are provided with spacings in tangential direction on a part of circumferential surface having the same radius of curvature on inner wall of the space;
(5) a swirling type micro-bubble generating system according to one of (1) to (4) above, wherein a plurality of pressure liquid inlets are provided with spacings in tangential direction on a part of circumferential surface having different radii of curvature on inner wall of the space;
(6) a swirling type micro-bubble generating system according to one of (1) to (5) above, wherein the pressure liquid inlet is provided on a part of circumferential surface of inner wall near the bottom of the space;
(7) a swirling type micro-bubble generating system according to one of (1) to (6) above, wherein the pressure liquid inlet is provided on a part of circumferential surface of inner wall near a point halfway down of the space; and
(8) a swirling type micro-bubble generating system according to one of (1) to (7) above, wherein a baffle plate is arranged downstream of the swirling gas-liquid outlet.
In the other aspects, the present invention further provides:
(9) a swirling type micro-bubble generating system, comprising a liquid flow swirling introducing structure of a circular accommodation chamber on a lower flow base, a swirli
Armstrong Westerman & Hattori, LLP
Bushey C. Scott
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