[0001] The invention relates to an apparatus for dissolving gas into liquid.
[0002] In many industrial applications, gas solutions are usually needed. However, most
gases cannot easily dissolve in water. Generally, a gas solution would not achieve
the desired purpose if the concentration of the gas is too low. Without some special
processing procedures, a solution with low gas concentration cannot be used in real
application. Therefore, an apparatus for producing high concentration of gas solution
is desperately needed in commercial applications. An apparatus for producing gas solution
with high concentration can be implemented to different applications. Specifically,
solutions with high concentration of oxygen and carbon dioxide are useful for high-density
aquaculture, and solutions with high ozone concentration can be used in semiconductor
wafer cleaning. Generally, the ozone concentration has to be at least 50 ppm for practical
applications. These are only two examples of the many applications of solutions with
high concentration of gas.
[0003] A widely used method for dissolving gas in water is to introduce gas into water through
an orifice placed within the water. This method increases surface contact area between
gas and water, and accordingly increases the rate of gas dissolving in water. Physical
methods, such as lowering the temperature of water, and increasing the pressure in
an enclosure containing the water and gas, may be applied to increase the rate of
gas dissolving in water. Chemical reactions between the dissolved gas and the liquid
medium, or reactions between the gas and other solutes dissolved within the liquid,
may also increase the rate of gas dissolving in liquid; the effect, however, is not
within the scope of the present invention, and thus is not to be discussed in this
specification.
[0004] In addition to the methods by which increasing temperature and pressure is used,
researchers have constantly been in search for other methods for increasing rate of
gas dissolving in liquid at reasonable costs. The present invention is directed to
a method of dissolving gas in liquid at low cost.
Summary of Invention
[0005] The object of the present invention is to provide an apparatus for mixing liquid
and gas, in which not only the methods of lowering the temperature of liquid and increasing
pressure of liquid/gas are used, measures of introducing gas at negative pressure
and using liquid whirlpool to trap the bubbles formed therein are also applied in
order to obtain higher rate of gas dissolving in the liquid.
[0006] The specific measure adopted in the present invention is to introduce the gas generated
by a gas generator to a mixer in which a valve is used for regulating the gas flowing
into the mixer. The mixer comprises primarily a gas expansion chamber and a device
similar to a Venturi tube. One of the examples was described in U.S. application serial
number 09/669,956, filed on September 26, 2000, and hereinafter is generally referred
to as quasi-Venturi tube. The 09/668,956 application is incorporated as part of the
subject application as reference, in which the quasi-Venturi tube is described to
pass longitudinally through an expansion chamber. In the present invention, a pump
is used for pumping the fluid so that the fluid may circulate in the claimed apparatus.
When the fluid flows through the quasi-Venturi tube, a suction effect is generated.
Gas in the expansion chamber is sucked into the quasi-Venturi tube and carried away
by the fluid. At the beginning of the operation, the gas generated by the gas generator
is introduced into the expansion chamber. A valve is mounted at the inlet of the expansion
chamber to regulate the gas flowing into the expansion chamber so that the quasi-Venturi
tube draws in the gas in a rate greater than the flow rate of the gas into the expansion
chamber. Accordingly, the gas is drawn into the quasi-Venturi tube at the state of
negative pressure, namely, at a pressure lower than the atmospheric pressure. The
gas forms bubbles at negative pressure in the fluid flowing through the quasi-Venturi
tube. The bubble-containing fluid is then introduced into an inner tank of a tank
enclosure which further comprises an outer tank, and generates whirlpool in the inner
tank. Due to the pressure of the ambient liquid, the size of the bubbles under negative
pressure would further decrease, and accordingly the buoyancy is reduced. In addition,
due to the effect of the whirlpool, the bubbles would not readily surface but remain
in the liquid for an extended period of time, which in turn contributes to higher
rate of gas dissolving in the liquid.
[0007] The pipe which supplies fresh liquid to the tank winds around the outer tank of the
tank enclosure, and finally inserts into the inner tank, where the fresh liquid is
blended with the bubble-carried fluid. The outer tank of the tank enclosure is connected
to a cooling system so that the fluid in the inner tank of the tank enclosure and
the fresh fluid in the winding pipe are cooled by the cooling water supplied by the
cooling system.
[0008] With the characteristics of the cooled fluid, the bubbles at negative pressure, and
the whirlpool, the apparatus according to the present invention may effectively increase
the rate of gas dissolved in the liquid, and thus the object of the present invention
is achieved.
[0009] In the present invention, since the mixer for generating bubbles at negative pressure
and the tank enclosure are available at low cost, the entire apparatus which comprises
such mixer and tank enclosure is also available at low cost. The cost effective installation
of such apparatus contributes to the industrial applicability of the present invention.
[0010] The gas generator of the present invention can be an ozone generator, and therefore
the apparatus according to the present invention can be easily converted to an apparatus
for producing ozonated water with high concentration of ozone.
Brief Description of the Drawings
[0011] These and other modifications and advantages will become even more apparent from
the following detailed description of a preferred embodiment of the invention and
from the drawings in which:
Fig. 1 shows the arrangement of the apparatus according to the present invention;
Fig. 2 is a schematic figure of the mixer of the apparatus shown in Fig. 1; and
Fig. 3 is a schematic figure of the tank enclosure of the apparatus shown in Fig.
1.
Detailed Description of the Invention (Preferred Embodiments)
[0012] The present invention now will be described more fully hereinafter with reference
to the accompanying drawings, in which a preferred embodiment of the invention is
shown.
[0013] As shown in Fig. 1, the apparatus according to the present invention comprises primarily
a gas generator 1, a mixer 20, a tank enclosure 30, and a pump 5.
[0014] The gas generator 1 is connected to a gas inlet 26 of the mixer 20 by a gas pipe
44. A valve 6 is arranged at the gas inlet 26 of the mixer 20.
[0015] As shown in Fig. 2, the mixer 20 comprises: a container 22 and a quasi-Venturi tube
24. The container 22 is an axially extended enclosure with one end provided with the
gas inlet 26. The gas inlet 26 is further provided with the valve 6 for regulating
the flow rate of the incoming gas. The quasi-Venturi tube 24 has one end being a liquid
inlet port and the other end being a liquid outlet port, and is axially arranged in
the container 22 so that it passes through the container 22 from one end to the other
end thereof, as shown by the arrows in Fig. 2. A throat (not shown) is formed within
the tube 24 and is located generally in the midst thereof. A gas drawn-in port 28
is provided at a position on the wall of the tube 24, which is preferably distant
from the gas inlet 26 of the container 22. The space inside the container 22 but outside
of the quasi-Venturi tube 24 is referred to as an expansion chamber 23.
[0016] The quasi-Venturi tube 24 is connected to the tank enclosure 30 through a liquid/gas
tube 42 (Fig. 1). As shown in Fig. 3, the tank enclosure 30 primarily comprises an
inner tank 32, an outer tank 34, and a winding pipe 36. The inner tank 32 has an inner
tank wall 33; the outer tank 34 has an outer tank wall 35, which encloses the inner
tank 32. A space is formed between the two tank walls 33, 35. The winding pipe 36
starts with a fresh liquid inlet 9, which enters the outer tank 34 and then winds
around the inner tank wall 33, preferably in helical manner, and subsequently enters
the inner tank 32, and ends at a fresh liquid inlet 15. The bottom of the tank enclosure
30 is provided with a liquid/gas output line 38, which is further connected to the
inlet of the pump 5.
[0017] The outer tank 34 of the tank enclosure 30 is provided with a cooling water inlet
8 near the bottom thereof and is provided with a cooling water outlet 16 near the
top thereof.
[0018] The tank enclosure 30 is further provided with an internal cooler 10 at the top center
thereof. The internal cooler 10 is provided with cooling water circulating pipes,
such as an auxiliary cooling water feeding pipe 13 and an auxiliary cooling water
discharging pipe 14., arranged near the liquid surface inside the tank enclosure 30.
[0019] The tank enclosure 30 is optionally provided with an overflow exit 11 near the top
thereof so as to prevent the liquid level from exceeding a predetermined height. A
thermometer 12 is optionally provided to the inner tank 32 for monitoring the temperature
therein.
[0020] During operation, the fluid is pumped by the pump 5 to flow through the quasi-Venturi
tube 24 in the mixer 20 where a suction effect is thus created. The gas in the container
22 would be drawn into the quasi-Venturi tube 24 via the gas drawn-in port 28 due
to the suction effect. The gas produced by the gas generator 1 enters container 22
via gas pipe 44, and diffuses therein. The valve of the gas pipe 44 regulates the
gas flow so that the gas flow rate is lower than the rate of the gas drawn into the
quasi-Venturi tube 24, so as to maintain a negative pressure in the expansion chamber
23.
[0021] The location of the gas inlet 26 of the container 22 and the location of the gas
drawn-in port 28 are near the opposite ends of the container 22, respectively. With
the arrangement, the gas can fully diffuse within the expansion chamber 23 before
being drawn into the quasi-Venturi tube 24, and the pressure at the gas drawn-in port
28 can remain stable. The stable pressure facilitates the bubbles to be mixed in the
liquid uniformly.
[0022] With the suction effect of the quasi-Venturi tube 24 and the flow regulation of the
valve 6, the gas enters the quasi-Venturi tube 24 at negative pressure, and bubbles
will be generated in the liquid at negative pressure (in relation to the atmospheric
pressure). The volume of the bubbles at negative pressure would further decrease under
the liquid pressure, and in turn reduce the buoyancy of the bubbles. The reduced buoyancy
would allow the bubbles to be trapped in the liquid for an extended period of time.
In other words, the bubbles would not emerge from the liquid and escape. The trapped
bubbles facilitate the gas to dissolve in the liquid.
[0023] The liquid which carries the bubbles flows out of the mixer 20 and proceeds to enter
the inner tank 32 of the tank enclosure 30 via the liquid/gas pipe 42. The liquid/gas
pipe 42 is preferably divided into two paths before entering the tank enclosure 30.
The divided pipes have outlets 17, 18 arranged in the inner tank 32 in parallel, horizontal
manner, and in opposite directions. When liquid flows out from the divided pipes and
enters the inner tank 32, the flow of the liquid creates a torque. The torque and
the downward flow exiting from the liquid/gas output line 38 contribute to forming
a whirlpool in the inner tank 32. The whirlpool enables the bubbles to rotate in the
liquid, and the bubbles will suspend in the liquid for an extended period of time.
These promote the gas to dissolve in the liquid.
[0024] The outer tank 34 of the tank enclosure 30 is supplied with cooling water from a
cooling system. The cooling water enters the tank enclosure 30 from near the bottom
thereof via the cooling water inlet 8, and flows out from near the top thereof via
the cooling water outlet 16. The cooling water is used for cooling the liquid in the
inner tank 32 and the fresh liquid flows along the winding pipe 36.
[0025] The fresh water is supplied from outside of the tank enclosure 30 via the fresh liquid
inlet 9, and flows along the winding pipe 36 which winds around the inner tank wall
33. The fresh water enters the inner tank 32 near the top thereof via the fresh liquid
inlet 15 and is mixed with the bubble-carrying liquid. The fresh liquid, as flowing
along the winding pipe 35, is cooled by the cooling water in the outer tank 34 so
that the temperature thereof can be lowered to provide a higher capability of dissolving
gas as it is mixed with the liquid in the inner tank 32.
[0026] The internal cooler 10 is arranged near the top of the inner tank 32. Inside the
internal cooler 10, cooling water is circulating for cooling the liquid inside the
inner tank 32. The cooler 10 can be a spherical shape and be adjustably arranged at
a location about the same level as the surface of the liquid at the center of the
inner tank 32. The internal cooler 10 is arranged to assist the cooling of the liquid
contained in the inner tank 32, and also to fill in the cavity formed in the center
of the whirlpool in the inner tank 32 so that the air is prevented from contacting
the liquid, and thus prevents air from dissolved in the liquid. With air dissolved
in the liquid, the rate of the gas to be dissolved (such as ozone) in the liquid would
be adversely affected.
[0027] The gas/liquid flowing out of the tank enclosure 30 can be extracted for use. In
the installation shown in Fig. 1, the gas/liquid is extracted via a liquid/gas mixture
outlet 2 arranged between the pump 5 and the mixer 20. Prior to the outlet 2, a liquid/gas
mixture outlet valve 4 and a micro bubble filter 3 are optionally mounted in order
to regulate the flow rate and to remove any suspended micro-bubbles that remain in
the liquid.
[0028] It is known that water with high ozone concentration (80 ppm) has been widely applied
to semiconductor water cleaning. With the gas generator 1 replaced with an ozone generator,
the apparatus according to the present invention can be converted to one for producing
ozone water of high ozone concentration.
[0029] With the construction and the operation as described above, the gas to be dissolved
in the liquid forms bubbles at negative pressure. The bubbles are characterized in
smaller size and less buoyancy in the liquid, which in turn may be retained in the
liquid for an extended period of time. In addition, the whirlpool generated in the
liquid helps retain the bubbles in the liquid. With the negative pressure and whirlpool
effects, the capability of the liquid for dissolving gas would significantly improve
if the liquid has already been under low temperature.
[0030] It will thus be seen that the invention efficiently attains the objects set forth
above, among those made apparent from the preceding description. Since certain changes
may be made in the above constructions without departing from the scope of the invention,
all matter contained in the above description or shown in the accompanying drawings
are intended to be interpreted as illustrative and not in a limiting sense.
1. An apparatus for dissolving gas into liquid, comprising:
a mixer comprising:
an axially extending container, having a gas inlet and a valve for regulating flow
rate of gas entering the container;
a quasi-Venturi tube axially arranged in the container, with one end of the quasi-Venturi
tube being a liquid inlet port and the other end being a liquid outlet port, the quasi-Venturi
tube having a tube wall being provided with a gas drawn-in port;
a tank enclosure, comprising:
an inner tank having a wall;
an outer tank having a wall enclos the inner tank and forming a space between the
wall of the inner tank and the wall of outer tank;
a winding pipe having an inlet and an outlet and extending from outside to inside
of the outer tank and winding around the inner tank and passing through the wall of
the inner tank with the outlet arranged inside of the inner tank;
a liquid/gas output line provided at a bottom of the tank enclosure;
a liquid/gas pipe with one end thereof connecting to the liquid outlet port of the
quasi-Venturi tube and the other end thereof connecting to the bottom of the tank
enclosure and inserting into inside of the tank enclosure so that the liquid flowing
out of the liquid/gas pipe forms a whirlpool inside the tank enclosure;
a pump having an outlet port connecting to the liquid inlet port of the quasi-Venturi
tube and an inlet port connecting to the liquid/gas output line; and
a liquid/gas mixture outlet provided between the outlet port of the pump and the liquid
inlet port of the quasi-Venturi tube.
2. The apparatus according to Claim 1, wherein the tank enclosure is provided with a
cooling water inlet and a cooling water outlet at a vicinity of each of a bottom and
top , respectively, of the tank enclosure.
3. The apparatus according to Claim 2, further comprising an internal cooler, the internal
cooler having a cooling water circulating pipe adjustably arranged near liquid surface
inside the tank enclosure.
4. The apparatus according to Claim 3, wherein the internal cooler has a shape of a hollow
sphere.
5. The apparatus according to Claim 1, 2, 3 or 4 wherein the gas inlet of the container
of the mixer is installed near one end of the container, and the gas drawn-in port
is installed at the location distal from the gas inlet.
6. The apparatus according to Claim 1, 2, 3, 4 or 5 wherein the liquid/gas pipe is divided
into two pipes after extending out from quasi-Venturi tube, and the two pipes insert
into the inside of the tank enclosure from the bottom thereof, the two pipes having
outlets that are oriented in parallel but in opposite directions.
7. The apparatus according to any one of the preceding claims, wherein the winding pipe
winds around the tank enclosure in helical manner.
8. The apparatus according to any one of the preceding claims, further comprising a gas
generator connected to the valve of the container.
9. The apparatus according to Claim 8, wherein the gas generator is an ozone generator.