Gas dissolution accelerating device

A gas dissolution accelerating device with a simple structure efficiently increases the concentrations of oxygen dissolved in deep water, such as at lake bottoms. A gas dissolution accelerating device includes a cylindrical member located parallel to a vertical direction when installed, a box member having an opening facing downward when installed, and a fixing unit for fixing the box member to a diffuser. The box member includes a top plate having a cone-shaped protrusion protruding inward and a through-hole receiving the cylindrical member. The fixing unit includes a flat attachment plate having an upper surface onto which the box member is mounted, a pair of halved banding members for clamping a feeding pipe of the diffuser, and rod-shaped connecting members connecting the attachment plate to the banding members.

BACKGROUND OF INVENTION

Field of the Invention

The present invention relates to a gas dissolution accelerating device used in combination with a diffuser that is installed mainly at a lake, an aquafarm, or a sewage plant to increase the concentration of a target gas dissolved in a liquid. In particular, the invention relates to a gas dissolution accelerating device with a simple structure that drastically increases the concentration of a target gas dissolved in a liquid.

Background Art

To increase the concentrations of oxygen dissolved in water at lakes or other places, diffusers may be installed, for example, at the bottoms of lakes to release air into water. However, simply supplying air into water has a limited effect of increasing the concentrations of oxygen dissolved in water.

In response to this, for example, Patent Literature 1 entitled SEWAGE TREATMENT DIFFUSER describes a diffuser that can greatly increase the dissolved oxygen concentrations at sewage treatment facilities or sanitation facilities.

The structure described in Patent Literature 1 includes a strip plate twisted about the centerline in the plate-width direction and having cutouts located at predetermined intervals in the longitudinal direction and extending in the plate-width direction, a mixing pipe containing the strip plate, and an air pipe located at the lower end of the mixing pipe.

When air is supplied from the air pipe to the mixing pipe in this sewage treatment diffuser, the air entrains the surrounding sewage into the mixing pipe, through which the air and the sewage mix while being stirred along the plate. This structure thus increases the dissolved oxygen in the sewage.

The structure described in Patent Literature 2 entitled GAS-LIQUID CONTACTOR is simple and improves the efficiency of oxygen dissolution.

The structure described in Patent Literature 2 includes a reaction tank containing a diffuser in its lower portion and a baffle located with a clearance from the tank wall and thus located near the liquid level in the tank to allow air bubbles ascending in a liquid to collide with the baffle.

This structure allows air bubbles ascending in the liquid to burst at the baffle and disperse along the lower surface of the baffle to the side plates until escaping through the clearance between the baffle and the tank wall into the atmosphere. Thus, the air bubbles remain in contact with the liquid in the tank for an extended period of time with an increased area of contact, improving the efficiency of oxygen dissolution in the liquid in the reaction tank.

CITATION LIST

Patent Literature

Patent Literature 1: Japanese Unexamined Patent Application Publication No. 7-39893

Patent Literature 2: Japanese Unexamined Patent Application Publication No. 10-263582

In deep water at the bottoms of lakes, for example, aquatic organisms consume oxygen dissolved in water. This increases the ratio of gases other than oxygen dissolved in water. Such gases have higher partial pressures at greater depths of water. At greater depths of water as described above, the diffusers described in Patent Literatures 1 and 2, which are installed in water to simply generate air bubbles containing oxygen, cannot increase dissolved oxygen sufficiently by exchanging gases other than oxygen dissolved in water with oxygen.

SUMMARY OF INVENTION

In response to the above issue, one or more aspects of the present invention are directed to a gas dissolution accelerating device with a simple structure that can efficiently increase the concentrations of oxygen dissolved in deep water, such as at the bottoms of lakes.

A gas dissolution accelerating device according to one or more aspects of the present invention is to be installed above a diffuser and includes a box member having an opening facing downward when installed and including a top plate with a through-hole, and a cylindrical member located parallel to a vertical direction when installed. The cylindrical member is received in the through-hole with a length extending downward from the top plate falling within a depth of the box member.

In the gas dissolution accelerating device with the above structure, many fine air bubbles generated by the diffuser ascend while entraining the surrounding liquid, and are trapped in the box member. The trapped air bubbles are clustered at the uppermost area of the liquid inside the box member to form liquid bubbles. In contrast, air bubbles reaching the lower end of the cylindrical member are not trapped in the box member but ascend through the cylindrical member while being clustered, and overflow through the upper end. The gas supplied as air bubbles forms a gas phase inside an upper space of the box member. The liquid bubbles are then exposed to the gas and burst in the gas phase.

The gas phase inside the box member gradually expands as the gas in the form of air bubbles is continuously supplied from the diffuser. However, the gas can no longer fill the box member when the interface between the gas phase and the liquid phase forms at the lower end of the cylindrical member. When air bubbles continue to be supplied to the box member, the air bubbles turn into liquid bubbles and burst in the gas phase. The excess gas from the gas phase again turns into air bubbles, which flow into the cylindrical member through the lower end.

The gas in the box member receives the water pressure at the depth of water. The gas components are then exchanged with the gas in the liquid films of the liquid bubbles under their respective partial pressures. When the liquid films lack sufficient oxygen, for example, oxygen inside and outside the liquid bubbles is absorbed into the liquid films, forcing other gases in the same amount as the absorbed oxygen to release from the liquid films. In the aspect of the present invention, the gas supplied from the diffuser comes in contact with the liquid films in the box member to accelerate dissolution of the gas in the liquid forming the liquid films.

A gas dissolution accelerating device according to one or more aspects of the present invention is the gas dissolution accelerating device according to the first aspect in which the box member has, at a position excluding the through-hole in the top plate, a cone-shaped protrusion that smoothly protrudes inward, and has a height falling within the length of the cylindrical member extending downward from the top plate.

In the gas dissolution accelerating device with the above structure, liquid bubbles formed by air bubbles collide with the tip of the protrusion and burst. The liquid in the liquid films ascends while spreading along the side surface of the cone-shaped protrusion again into thin liquid films. These liquid films also absorb gas components in the gas in the gas phase under their respective partial pressures, thus forcing excess gas components dissolved in the liquid films to be released outside.

A gas dissolution accelerating device according to one or more aspects of the present invention is the gas dissolution accelerating device according to the second aspect that includes a first box member and a second box member each having the same structure as the box member described above and each including the cylindrical member and the protrusion. The second box member is located below the first box member with an upper end of an opening of the cylindrical member located immediately below a tip of the protrusion in the first box member.

In the above structure, clustered air bubbles ascending through the cylindrical member located at the second box member forcefully overflow the cylindrical member through the upper end, and collide with the tip of the protrusion in the first box member while entraining a large amount of surrounding liquid and burst again into larger, thin liquid films. The cylindrical member located at the second box member gathers air bubbles reaching its lower end and directs such air bubbles immediately below the tip of the protrusion in the first box member.

In the above aspect of the present invention, air bubbles reaching the gas phase form liquid bubbles in the second box member, in addition to the first box member. The liquid bubbles then collide with the tip of the protrusion and burst to form thin liquid films along the side surface of the protrusion. Additionally, more liquid bubbles densely collide with the tip of the protrusion in the first box member than in the structure according to the second aspect. The larger liquid films form after the burst of the liquid bubbles than in the second aspect of the present invention. The structure according to the third aspect thus further accelerates the dissolution of the gas supplied from the diffuser into the liquid films, enhancing the effect of the first aspect.

A gas dissolution accelerating device according to one or more aspects of the present invention is the gas dissolution accelerating device according to the third aspect in which the cylindrical member located at the second box member is received in the through-hole with the upper end protruding upward from the top plate.

In the gas dissolution accelerating device with the above structure, the upper end of the cylindrical member located at the second box member is nearer the tip of the protrusion in the first box member than the cylindrical member according to the third aspect. The cylindrical member located at the second box member thus more reliably gathers air bubbles reaching the lower end and directs such air bubbles immediately below the tip of the protrusion in the first box member.

A gas dissolution accelerating device according to one or more aspects of the present invention is the gas dissolution accelerating device according to the fourth aspect in which the cylindrical member located at the second box member is received in the through-hole in the top plate with the upper end located below a lower end of the cylindrical member located at the first box member.

When the upper end of the cylindrical member located at the second box member is placed in the gas phase inside the first box member, air bubbles fed through the upper end of the cylindrical member entrain less liquid. The liquid bubbles formed by such air bubbles are thus less likely to form larger liquid films after colliding with the tip of the protrusion and bursting. In contrast, the above structure includes the second box member including the cylindrical member with the upper end located below the interface between the gas phase and the liquid phase at the level of the lower end of the cylindrical member when no more gas can be stored in the first box member. The cylindrical member located at the second box member thus has the upper end located in the liquid phase of the first box member.

More specifically, the structure according to the above aspect of the present invention allows air bubbles overflowing the cylindrical member located at the second box member through the upper end to forcefully ascend in the liquid phase while entraining a large amount of surrounding liquid. The air bubbles then form liquid bubbles and forcefully collide with the tip of the protrusion in the first box member to form larger, thin liquid films along the side surface of the cone-shaped protrusion.

A gas dissolution accelerating device according to one or more aspects of the present invention is the gas dissolution accelerating device according to any one of the third to fifth aspects further including rod-shaped connectors. The first box member and the second box member each have holders on side plates opposing each other, and each of the holders receives an upper end of one of the connectors and/or a lower end of another one of the connectors.

The gas dissolution accelerating device with the above structure includes the first box member and the second box member that are stacked vertically and connected to each other with the connectors in the holders, in addition to the effect of any one of the third to fifth aspects.

A gas dissolution accelerating device according to one or more aspects of the present invention is the gas dissolution accelerating device according to any one of the third to sixth aspects in which the cylindrical member located at the second box member has a slit with an intended width on a side surface and received in the through-hole in the top plate with an uppermost end of the slit located below a tip of the protrusion in the second box member.

When a large amount of air bubbles is supplied from the diffuser to the second box member, the cylindrical member with an inlet for the air bubbles at the lower end alone can cause the air bubbles trapped in the second box member to intensely agitate up and down the interface between the gas phase and the liquid phase in the second box member. This prevents smooth flow of air bubbles into the cylindrical member, and causes the air bubbles to intermittently overflow the cylindrical member through the upper end. In this case, liquid bubbles formed by such air bubbles do not collide with the tip of the protrusion continuously, possibly preventing formation of larger, thin liquid films.

In contrast, the structure according to the above aspect includes the cylindrical member located at the second box member with slits on the side surface. This structure allows fine air bubbles to flow into the cylindrical member through the slits, and allows large air bubbles that cannot pass through the slits to flow into the cylindrical member through the lower end. In this structure, the interface between the gas phase and the liquid phase described above is less likely to be agitated up and down, thus allowing smooth flow of air bubbles into the cylindrical member through the lower end or through the slits. The air bubbles continuously overflowing the cylindrical member through the upper end then form liquid bubbles and collide with the tip of the protrusion in the first box member.

In the structure according to the above aspect, air bubbles excessively supplied from the diffuser to the second box member are less likely to intensely agitate up and down the interface between the gas phase and the liquid phase in the second box member. In addition to the effect of any one of the third to sixth aspects, this structure thus allows air bubbles to smoothly flow into the cylindrical member and continuously overflow the cylindrical member through the upper end to form liquid bubbles and constantly collide with the tip of the protrusion in the first box member.

As described above, the gas dissolution accelerating device according to the first aspect is located above the diffuser that may be installed in deep water such as at the bottoms of lakes, and thus accelerates dissolution of the gas supplied from the diffuser and efficiently increases the concentrations of the gas dissolved in the liquid.

The gas dissolution accelerating device according to the second aspect allows the gas components in the gas in the gas phase to dissolve, under their respective partial pressures, in the thin liquid films that form along the side surface of the cone-shaped protrusion after the liquid bubbles burst in the gas phase of the box member, in the same manner as in the liquid films of the liquid bubbles. The above structure thus more efficiently increases the concentrations of the gas from the diffuser to dissolve in the liquid, further enhancing the effect of the first aspect.

The gas dissolution accelerating device according to the third aspect allows air bubbles reaching the gas phase to form liquid bubbles and collide with the tip of the protrusion and burst to form thin liquid films in the second box member, in the same manner as in the first box member according to the second aspect of the present invention, and further allows the air bubbles in the first box member to overflow the cylindrical member located at the second box member through the upper end and densely collide with the tip of the protrusion and burst to form larger, thin liquid films along the side surface of the protrusion. The gas dissolution accelerating device according to the above aspect allows the gas components in the gas in the gas phase to dissolve in the liquid under their respective partial pressures in the first box member and the second box member. This structure further increases the concentrations of the gas from the diffuser to dissolve in the liquid, further enhancing the effect of the first aspect.

The gas dissolution accelerating device according to the fourth aspect accurately directs air bubbles reaching the lower end of the cylindrical member located at the second box member immediately below the tip of the protrusion in the first box member through the cylindrical member, and allows the gas components in the gas in the gas phase of the first box member to dissolve in the liquid films that form after the liquid bubbles collide with the protrusion. This structure thus efficiently increases the concentrations of the gas dissolved in the liquid, further enhancing the effect of the third aspect.

The gas dissolution accelerating device according to the fifth aspect allows air bubbles to overflow the cylindrical member through the upper end in the gas phase of the second box member and forcefully collide with the tip of the protrusion in the first box member, without decelerating while ascending. This forms larger, thin liquid films along the side surface of the cone-shaped protrusion. This structure allows the gas components in the gas phase to dissolve in the liquid films, and efficiently increases the concentrations of the gas components dissolved in the liquid, further enhancing the effect of the fourth aspect.

The gas dissolution accelerating device according to the sixth aspect includes the first box member and the second box member that are installed in a stable manner, in addition to the effect of any one of the third to fifth aspects.

The gas dissolution accelerating device according to the seventh aspect allows larger, thin liquid films to form easily along the side surface of the protrusion in the first box member when air bubbles are excessively supplied from the diffuser to the second box member and liquid bubbles formed by such air bubbles overflowing the cylindrical member located at the second box member through the upper end collide with the protrusion in the first box member and burst. This structure further accelerates the dissolution of the gas supplied from the diffuser in the liquid and more efficiently increases the concentrations of the gas dissolved in the liquid, in addition to the effect of any one of the third to sixth aspects.

DETAILED DESCRIPTION

A gas dissolution accelerating device according to embodiments of the present invention will be described in detail with reference toFIGS. 1 to 5. The gas dissolution accelerating device according to one or more embodiments of the present invention is installed for use above a diffuser in a liquid to be treated. The gas dissolution accelerating device will thus be hereafter described using directional terms including an upper end and a lower end, based on an actual use of the gas dissolution accelerating device with a box member open downward and cylindrical members parallel to the vertical direction. A liquid to be treated may be other than water. Thus, liquid bubbles and liquid films are used rather than water bubbles and water films.

First Embodiment

FIG. 1is an example external perspective view of a gas dissolution accelerating device according to an embodiment of the present invention.FIGS. 2A and 2Care cross-sectional views respectively taken along lines A-A and B-B inFIG. 1.FIG. 2Bis an enlarged external perspective view of a cylindrical member.FIG. 2Cis a view of a box member inFIG. 2Athat is installed in water. InFIGS. 2A and 2C, a diffuser and a fixing unit are not shown. InFIG. 2C, connectors are indicated by dashed lines for describing the structure of the holders on the side plates of the box member.

FIGS. 3A and 3Bare diagrams describing the movement of air bubbles supplied from the diffuser into the cylindrical members.FIG. 3Ashows the diffuser located below the box member inFIG. 2B, andFIG. 3Bis an enlarged view of the cylindrical member inFIG. 3A. InFIG. 3A, a fixing unit is not shown.

As shown inFIGS. 1 to 2C, a gas dissolution accelerating device1aincludes cylindrical members2installed to be parallel to the vertical direction, a box member3having an opening facing downward, and a fixing unit5for fixing the box member3to a diffuser4. The term being parallel to or to be parallel to the vertical direction in embodiments and aspects of the present invention includes being substantially parallel to the vertical direction.

The box member3includes a top plate6having cone-shaped protrusions6athat smoothly protrude inward. The top plate6has through-holes6b(refer toFIG. 2A) in flat areas excluding the protrusions6a. The cylindrical members2are received in the through-holes6bperpendicularly to the top plate6and fixed to the box member3. The box member3also includes a pair of side plates7parallel to each other. The side plates7include holders7aat opposing positions for each receiving an upper end or a lower end of a rod-shaped connector11(refer toFIG. 2C).

For example, two box members3stacked vertically may be connected to each other with such connectors11each having an upper end held by an upper holder7aand a lower end held by a lower holder7afacing the upper holder7a. The box members3in the gas dissolution accelerating device1ainclude the holders7ato connect multiple box members3installed vertically with the connectors11in a stable manner.

The diffuser4includes a gas source (not shown) such as a blower, a feeding pipe4awith one end connected to the gas source, and a porous diffusing cylinder4bconnected to the other end of the feeding pipe4a. Air is supplied from the air source to the porous diffusing cylinder4bthrough the feeding pipe4a.

The fixing unit5includes a flat attachment plate8having an upper surface8aonto which the box member3is to be mounted, a pair of halved banding members9for clamping the feeding pipe4a, and rod-shaped connecting members10for connecting the attachment plate8to the banding members9.

The banding member9includes a semicircular clamping portion curved along the outer circumference of the feeding pipe4aand attachment portions extending outward from the ends of the clamping portion in the radial direction of the feeding pipe4a. The attachment portions each have a bolt hole. The banding members9are fastened to the feeding pipe4awith bolts received in the bolt holes in the attachment portions.

The side plates7of the box member3each have an edge7bbent outward at a right angle. The edge7bhas screw holes7cto receive screws to fasten the box member3to the attachment plate8.

As shown inFIGS. 2A to 2C, each cylindrical member2is received in the through-hole6bin the top plate6to have an upper end2aprotruding upward from the top plate6. The cylindrical member2has a length L1extending downward from the top plate6shorter than a depth L2of the box member3and longer than a height L3of the protrusion6a. More specifically, the cylindrical member2received in the through-hole6bhas the length L1extending downward from the top plate6falling within the depth L2of the box member3. The protrusion6ahas the height L3falling within the length L1of the cylindrical member2extending downward from the top plate6.

The cylindrical member2has four slits2don a side surface2c. The slits2dare equiangularly spaced along the circumference each with an intended width and a length L4from a lower end2b. The relationship among the length L4of the slit2d, the length L1of the cylindrical member2extending downward from the top plate6, and the height L3of the protrusion6ais expressed by the formula (1) below. In other words, the cylindrical member2is received in the through-hole6bin the top plate6with the uppermost ends of the slits2d(points away from the lower end2bby the length L4) located below the tip of the protrusion6a. The cylindrical member2may have any number of slits2dwith any width, other than the examples described in the present embodiment.
L4<L1−L3Formula 1

The gas dissolution accelerating device1ashown inFIG. 1is installed in water at a lake or another place to have the top plate6of the box member3substantially horizontal. When gas such as oxygen or air is supplied to the diffuser4with a blower, for example, many air bubbles form through the porous diffusing cylinder4b.

The air bubbles are trapped in the box member3located above the diffuser4, and form a gas phase13above an interface at the level of the uppermost ends of slits2din the box member3. The interface between the gas phase13and the liquid phase in the box member3is hereafter simply referred to as an interface12.

As shown inFIG. 3A, many fine air bubbles14generated by the diffuser4ascend while entraining the surrounding water, and then are trapped in the box member3. However, air bubbles14reaching the lower end2bof the cylindrical member2are not trapped in the box member3but ascend through the cylindrical member2while being clustered, and then overflow through an upper end2a.

The air bubbles14trapped in the box member3burst at the uppermost area of the water inside the box member3and enter the gas phase13. The clustered air bubbles14reach the gas phase13and form liquid bubbles15, and then are exposed to the gas and burst in the gas phase13.

The air bubbles14continuously supplied to the box member3from the diffuser4gradually expand the space defining the gas phase13. This lowers the level of the interface12. The box member3can store a limited amount of gas. Once the interface12reaches the level of the uppermost ends of slits2don the cylindrical member2, air bubbles14freshly supplied to the box member3form liquid bubbles and burst in the gas phase13, but cannot remain in the gas phase13. The excess gas re-forms air bubbles14and flows into the cylindrical member2through the lower end2b.

The gas thus stored in the box member3receives the water pressure at the depth of the water. The gas components in the gas are absorbed in the liquid films of the liquid bubbles15under their respective partial pressures, and then excess gas components dissolved in the liquid films are released outside. When the liquid films lack sufficient oxygen, for example, oxygen inside and outside the liquid bubbles15is absorbed in the liquid films, and other gases are released from the liquid films in the same amount as the oxygen absorbed.

More specifically, the gas dissolution accelerating device1ais installed in deep water, such as at the bottom of a lake, and oxygen or air is supplied from the diffuser4to the box member3. The gas stored in the box member3receives the water pressure at the depth of the water. The water in such a place may contain gases other than oxygen with increased concentrations from aquatic organisms consuming the oxygen dissolved in the water. However, the other gases dissolved in the liquid films of the liquid bubbles15are exchanged with oxygen under their respective partial pressures as described above. The gas dissolution accelerating device1alocated above the diffuser4, which may be installed in deep water, can accelerate oxygen dissolution in water to efficiently increase the dissolved oxygen concentrations.

Air bubbles14entraining the surrounding water ascend to the gas phase13to form liquid bubbles, which collide with the tips of the protrusions6aand burst. The liquid in the liquid films of the liquid bubbles15ascends while spreading along the side surfaces of the cone-shaped protrusions6a, as indicated by the dashed arrows, and re-form larger, thin liquid films. Similarly to the liquid films of the liquid bubbles15, these larger, thin liquid films also absorb gas components in the gas in the gas phase13under their respective partial pressures, and then excess gas components dissolved in the liquid films are released outside. This structure further increases the concentrations of oxygen dissolved in water.

The gas supplied from the diffuser4to the box member3in the form of air bubbles14may exceed the amount of gas storable in the box member3. In this case, the cylindrical member2with an inlet for air bubbles14at the lower end2balone can cause the air bubbles14trapped in the box member3to intensely agitate the interface12up and down. This may prevent smooth flow of the air bubbles14into the cylindrical member2, and cause the air bubbles14to intermittently overflow the cylindrical member2through the upper end2a.

In contrast, the gas dissolution accelerating device1aincludes the cylindrical member2with slits2don the side surface. This structure allows, as indicated by the solid arrows inFIG. 3B, fine air bubbles14to flow into the cylindrical member2through the slits2d, and large air bubbles14that cannot pass through the slits2dto flow into the cylindrical member2through the lower end2b. The gas dissolution accelerating device1athus allows air bubbles14to smoothly flow into the cylindrical member2, and to continuously overflow the cylindrical member2through the upper end2a.

Second Embodiment

FIG. 4Ais an external front view of a gas dissolution accelerating device according to a second embodiment of the present invention.FIG. 4Bis a cross-sectional view of the gas dissolution accelerating device shown inFIG. 4Ataken along a vertical plane including the center in the width direction.FIG. 5is a diagram describing the movement of air bubbles inFIG. 4B.FIG. 5shows a box member inFIG. 4Bthat is installed in water. More specifically,FIGS. 4B and 5respectively correspond toFIGS. 2C and 3Ain the first embodiment.

InFIG. 4B, the diffuser is not shown. InFIGS. 4A and 5, the fixing unit is not shown. The same components inFIGS. 1 to 3Bare given the same reference numerals and will not be described repeatedly.

As shown inFIGS. 4A and 4B, a gas dissolution accelerating device1bincludes three box members3ato3ceach having the same structure as the box member3in the gas dissolution accelerating device1ain the first embodiment. The box members3ato3care stacked at intended intervals in the vertical direction and connected to one another with the connectors11. The box member3bis located below the box member3awith the opening at the upper end2aof each cylindrical member2located at the box member3bimmediately below the tip of the corresponding protrusion6ain the box member3a. Likewise, the box member3cis located below the box member3bwith the opening at the upper end2aof each cylindrical member2located at the box member3cimmediately below the tip of the corresponding protrusion6ain the box member3b.

In the present embodiment, the three box members3ato3care provided. However, any number of box members may be used.

As shown inFIG. 5, in the gas dissolution accelerating device1bwith the above structure, clustered air bubbles14ascending through each cylindrical member2located at the box member3coverflow the cylindrical member2through the upper end2a, and are exposed to the gas in the gas phase13contained in the box member3band form liquid bubbles15. The liquid bubbles15then collide with the tip of the corresponding protrusion6ain the box member3band burst. Clustered air bubbles14ascending through each cylindrical member2located at the box member3boverflow the cylindrical member2through the upper end2a, and are exposed to the gas in the gas phase13contained in the box member3ato form liquid bubbles. The liquid bubbles then collide with the tip of the corresponding protrusion6ain the box member3aand burst.

The cylindrical members2located at the box member3ceach gather air bubbles14reaching the lower end2band direct such air bubbles14immediately below the tip of the corresponding protrusion6ain the box member3b. Likewise, the cylindrical members2located at the box member3beach gather air bubbles14reaching the lower end2band direct such air bubbles immediately below the tip of the corresponding protrusion6ain the box member3a.

In the gas dissolution accelerating device1b, air bubbles14reaching the gas phase13form liquid bubbles15in the box members3band3cas well, in addition to the box member3aas described above. The liquid bubbles15then collide with the tips of the protrusions6aand burst to form liquid films along the side surfaces of the protrusions6a. More liquid bubbles15densely collide with the tips of the protrusions6ain the box members3aand3bthan the liquid bubbles15in the gas dissolution accelerating device1a. Larger liquid films thus form after the burst of the liquid bubbles15than in the gas dissolution accelerating device1a. In the box member3c, liquid bubbles15collide with the tips of the protrusions6aand burst to form thin liquid films along the side surfaces of the cone-shaped protrusions6aas indicated by dashed arrows. In the box members3aand3b, larger liquid films than in the box member3cform along the side surfaces of the cone-shaped protrusions6aas indicated by solid arrows. The gas dissolution accelerating device1ballows other gases dissolved in the liquid films to be exchanged with oxygen under their respective partial pressures, thus enhancing the effect of the gas dissolution accelerating device1a.

In the gas dissolution accelerating device1b, the cylindrical members2at least located at the box members3band3care each received in the through-hole6bwith the upper end2aprotruding upward from the top plate6. The cylindrical members2located at the box member3cthus each have the upper end2alocated adjacent to the tip of the corresponding protrusion6ain the box member3b, and the cylindrical members2located at the box member3beach have the upper end2alocated adjacent to the tip of the corresponding protrusion6ain the box member3a. The cylindrical member2with the above arrangement gathers air bubbles14reaching the lower end2band directs the air bubbles14immediately below the tip of the corresponding protrusion6ain the box member located above in a more reliable manner than the cylindrical member2with the upper end2anot protruding upward from the top plate6.

When the cylindrical members2located at the box members3band3ceach have the upper end2aplaced in the gas phase13inside the box member3aor3b, air bubbles14fed through the upper end2aof each cylindrical member2located at the box members3band3ccan entrain less water. The air bubbles14, which form liquid bubbles, are thus less likely to form larger liquid films after colliding with the tip of the corresponding protrusion6ain the box members3aand3band bursting.

In the gas dissolution accelerating device1b, however, each cylindrical member2located at the box members3band3chas the upper end2alocated below the lower ends2bof the cylindrical members2located at the box members3aand3b(refer toFIG. 4B). Each cylindrical member2located at the box members3band3cthus has the upper end2alocated below the interface12at the level of the slits2don the cylindrical members2when no more gas can be stored in the box members3aand3b.

In the gas dissolution accelerating device1b, as shown inFIG. 5, air bubbles14overflowing the cylindrical members2located at the box members3band3cthrough the upper ends2aforcefully ascend in the liquid phase while entraining a large amount of surrounding water when the gas is excessively supplied from the diffuser4to the box members3ato3cbeyond their allowable capacity. The air bubbles14then form liquid bubbles in the gas phase13and forcefully collide with the tips of the protrusions6ain the box members3aand3b. This forms larger, thin liquid films along the side surfaces of the cone-shaped protrusions6ain the box members3aand3b.

For the cylindrical member2with the slits2don the side surface as described in the present embodiment, the cylindrical members2located at the box members3band3cmay each have the upper end2alocated below the uppermost ends of the slits2don the cylindrical members2located at the box members3aand3b.

In addition, the cylindrical members2located at the box members3ato3cin the gas dissolution accelerating device1bhave the slits2don the side surfaces. The gas dissolution accelerating device1bthus has the same effect as the gas dissolution accelerating device1adescribed with reference toFIG. 3Bin the first embodiment. More specifically, in the gas dissolution accelerating device1b, air bubbles14excessively supplied from the diffuser4to the box members3ato3care less likely to intensely agitate the interfaces12up and down. The air bubbles14thus smoothly flow into the cylindrical members2, and then continuously overflow the cylindrical members2located at the box members3band3cthrough the upper ends2ato form liquid bubbles and constantly collide with the tips of the protrusions6ain the box members3aand3b. This facilitates the liquid bubbles15to form thin liquid films along the side surfaces of the protrusions6awhen the liquid bubbles15collide with the tips of the protrusions6ain, in particular, the box members3aand3bin the gas dissolution accelerating device1b. The dissolved oxygen concentrations in water are thus increased more efficiently.

The present invention is applicable to efficient dissolution of a target gas not limited to oxygen in a target liquid.

REFERENCE SIGNS LIST