Title of Invention	DRAFT TUBE AND AIR BUBBLE TOWER
Abstract	DRAFT TUBE AND AIR BUBBLE TOWER

Full Text

FORM 2 THE PATENTS ACT, 1970 (39 Of 1970) COMPLETE SPECIFICATION (See Section 10, rule 13) DRAFT TUBE AND AIR BUBBLE TOWER KYOWA HAKKO KOGYO CO. LTD. of 6-1, 1-CHOME, CHIYODA-KU, TOKYO 100-8185, "JAPAN, JAPANESE Company The following specification particularly; describes the nature of the invention and the manner in which it is to be performed : - DRAFT TUBE AND BUBBLE COLUMN TECHNICAL FIELD OF THE INVENTION The present invention relates to a draft tube and a bubble 5" column. BACKGOUND ART An aerated stirred-tank or a bubble column having a draft tube has been used for gas absorption or cultivation of 10 microorganisms and the like so far. However, the prior aerated stirred-tank is required to have enough strength by thickening the wall of the tank (can) for putting solution therein and to have a bearing for an agitator because a motor for agitation (not shown) is provided above the 15 tank and the agitator is installed in the tank. Further, for cultivation of microorganisms, it is required to provide an equipment for keeping sterility of the axis of the agitator, which increases the installation cost. As a bubble column, for example, a bubble column shown in 20 Fig.21, has been already proposed. The bubble column is largely different from the aerated stirred-tank in that agitation and mixture of the solution contained in the tank (can) depends on the liquid flow caused by aeration. 25 . For example, the bubble column 301 has a tank (can) 302 for putting solution therein, a draft tube 303 provided in the tank. (can) 302, and a sparger 304 provided below the draft tube 303 in the tank (can) 302 in such amanner that air bubbles are supplied into the solution contained in the tank (can) 302 through plural 30 apertures 304h-" provided for the sparger 304 to agitate and mix the solution contained in the tank (can) 302. Generally, in the bubble column the height of the liquid surface (liquid level) in the tank (can) sometimes varies during operation because of evaporation accompanied by aeration and 35 addition of solution during operation. In case of the bubble column 30.1 shown in Fig.21, Which has the draft tube 303 in the tank (can) 302 containing the solution, when the liquid level of the solution in the tank (can) 302 becomes lower than the upper end of the draft tube 303, circulation of 40 the solution inside and outside of the draft tube 303 is interrupted, thereby deteriorating agitation of the solution. In order to solve the above-mentioned problems, the bubble column 401 shown in Fig.22 has been proposed. The bubble column 401 has apertures 403h at the upper part of a draft tube 403 provided in the tank (can) 302 for putting 5 solution therein. However, also in case of this bubble column 401, it is required to keep the liquid level above the apertures 403h in order to keep mixing performance. According to the bubble column 501 in Fig.23, a draft tube 10 503 is comprised of plural plates 503A-" so as to cause mixture and agitation by liquid circulation through the space between each one of the plural plates 503Aeyen when the liquid level of the solution contained in a tank (can) 302 varies. However, the draft tube 503 actually needs many welding members and its 15 construction becomes complicated, thereby causing a problem of high production cost, difficulty of keeping sterility in cultivation of microorganisms, and much labor for maintenance. Further, in general, the use of a bubble column accompanies a heat generation reaction and a heat absorption reaction so that 20 a cooling equipment or a heating equipment is provided inside or outside of the tank (can) of the bubble column so as to enable temperature control by heat exchanging. However, if the bubble column becomes large, heat transferring area per a unit volume of a heat exchanging equipment 25 for temperature control is hardly obtained. Therefore, for the fermentation or chemical reaction with large heat generation and large heat absorption, a large scale bubble column is problematic in that the heat transferring area is not sufficiently obtained, which restricts enlargement of the 30 bubble column. """ . According to the above-mentioned reasons, in the method where a cooling jacket is provided outside of the tank (can) of the bubble column, the volume of the tank".{can) of the bubble column has been limited to some cubic meters. 35 In a bubble column (501 shown in Fig.24, a heat exchanger 602 is provided outside of a tank (can) 302 and the solution in the tank (can) 302 is circulated into the heat exchanger 602 so as to keep uniform temperature of solution contained in the tank (can) 302, however, the bubble column 601 is problematic in that 40 the temperature in the tank (can) 302 does not become uniform. DISCLOSURE OF THE INVENTION- The present invention has been proposed in oi.der to solve the above-mentioned problems. The object of the present invention is to provide a draft tube by which a bubble column 5 is operated irrespective of the liquid level of the solution contained in a tank, which is excellent in the mixture performance and gas absorption performance of the solution contained in the tank, and by which the heat transfer area is easily obtained, and the maintenance and scale-up are facilitated, and to provide 10 a bubble column using the draft tube. The present invention relates to a draft tube provided in a bubble column, and the draft tube comprises a hollow pipe and has spacing gaps in whole peripheral surface. Since the draft tube has the spacing gaps in the whole 15 peripheral surface, if the draft tube is installed in the tank of the bubble column, the solution in the draft tube and the solution outside of the draft tube are circulated through the spacing gaps provided in the whole peripheral surface irrespective of the amount of solution contained in the tank. 20 \ Therefore, the bubble column having such a draft tube can be operated irrespective of the liquidl"level of the solution in the tank. Further, since the draft tube comprises a hollow pipe, the temperature of solution contained in the tank is effectively 25 controlled into a predetermined one" by circulating a heat-exchanging medium in the hollow pipe. The present invention also relates to the draft tube, the cross sectional shape of which is circle, oval or polygon. "The cross sectional shape" in this specification means the 30 shape of a cut surface of the draft tube when it is cut in a direction orthogonal to its center axis. The cross sectional shape may be any shape if the tube is functioned as a draft tube. The cross sectional shape may be circle, oval or square 35 including polygonal shapes like triangle, rectangle and do on. The present invention also relates to the draft tube in which a hollow pipe is wound spirally like a coil. Since the hollow pipe in the draft tube is wound spirally like a coil, if the draft tube is provided in the tank of the 40 bubble column, the medium for cultivation or the gas absorbing solution contained in the tank is circulated in and out of the draft tube via the spacing gaps formed in the whole peripheral surface of the draft tube even if the liquid level of the medium for cultivation or the gas absorbing solution in the tank is at any level. 5 Therefore, the bubble column with such a draft tube can be operated irrespective of the liquid level of the solution contained in the tank. Further, since the hollow pipe in the draft tube is spirally wound like a coil, it is easy to design and adjust the ratio of 10 the spacing gaps to the area of peripheral surface of the draft tube to be appropriate based on the winding number of the hollow pipe per a unit of length. Still further, if the draft tube is"provided in the tank of . the bubble column and a heat exchanging medium is circulated from 15 the bottom to the top in the hollow pipe;the solution contained in the tank of the bubble column i& effectively controlled to be a desired temperature. The present invention also relates to the draft tube in which a hollow pipe is bent in zigzag-. 20 \ Since the hollow pipe in the draft tube is bent in zigzag, if the a draft tube is provided in the tank"of the bubble column, the medium for cultivation or the gas absorbing solution contained in the tank is circulated in and out of the draft tube via the spacing gaps formed in the peripheral surface of the draft 25 tube even if the liquid level of the medium for cultivation or the gas absorbing solution in the tank is at any level. Further, since the hollow pipe in the draft tube is bent in zigzag, it is easy to design and adjust the ratio of spacing gaps to the area of the draft tube to be appropriate based on the bending 30 number of the hollow pipe per a unit of length. Still further, if the drott tube In provided ".in the lank of the bubble column and a heat exchanging.medium is circulated in the hollow pipe, the solution contained in the tank of the bubble column is effectively controlled to be:a desired temperature. 35 The present invention also relates to a draft tube in which plural units of draft tube comprised of the hollow pipe which is wound spirally like a coil are stacked in the tank for containing solution therein in the bubble column. Since a heat exchanging medium is circulated in each one of 40 plural draft tube units, the solution contained in the tank of the bubble column is effectively controlled to be a desired temperature. In this case, considering the heat exchange efficiency, the heat exchanging medium is preferably circulated from the bottom to the top in the hollow pipe constituting each one of plural draft tube units. 5 Because the heat exchanging medium is independently circulated in each draft tube unit, when the heat exchanging mediums circulating in the draft tube.units supplied under the same condition, the heat exchanging efficiency of each draft tube unit becomes the same. 10 Therefore, when the draft tube units are stacked up, the heat exchanging tubes are arranged vertically in a line, thereby preventing the solution in the tank from causing ununiformity of the temperature. Further, by using plural draft tube units, the amount of heat exchanging medium is increased to iinprove the 15 heat exchange ability. The present invention also relates to a draft tube in which plural units of draft tube comprised of the hollow pipe is bent in zigzag are stacked up in the tank containing solution in the bubble column. 20 !., In the draft tube, since plural draft tube units comprised of the hollow pipe bent in zigzag are stacked up so that a heat exchanging medium is circulated per each one of plural draft tube units. Therefore, if the heat exchanging mediums circulating in plural draft tube units are supplied under the same condition, 25 ,the heat exchanging efficiency of each draft tube unit becomes the same. r Hence, when the draft tube units-..>are stacked up, the heat exchanging tubes are arranged vertically in the tank, thereby reducing ununiformity of the temperature in the solution in the 30 tank. Further, by using plural draft: tube units, the amount of heat exchanging medium is increased to improve the heat exchange ability. The draft tube of the present invention also relates to a draft tube wherein" the ratio of spacing gaps to the area of the 35 whole peripheral surface of the draft tube is limited to 1 to 99 percent. The ratio of spacing gaps to the area of the whole peripheral surface of the draft tube is preferably limited to 10 to 90 percent. More preferably, it is ■limited to 25 to 50 percent. 40 The ratio of spacing gaps is obtained by the following formula; ratio of spacing gaps = the area of all spacing gaps between the hollow pipe forming the draft: tube / the nrcn of the pen" phoral surface of the draft tube x 100 The ratio of spacing gaps can be set at any suitable values 5 depending on the size of the tank of the bubble column, the volume of solution contained in the tank, the circulation method of the solution and so on. However, it is not preferable to limit the ratio of spacing gaps to extremely low, for example 0%, because the circulation 10 of the solution inside and outside of the draft tube via the peripheral surface of the draft tube is completely interrupted. On the other hand, it is not preferable to limit the ratio of spacing gaps to extremely high, because the existence of the draft tube hardly has meanings so that the bubble column has the 15 same effect as that without having the draft tube in the tank. Considering the above, the ratio of spacing gaps on the peripheral surface of the draft tube is limited.preferably to the range mentioned above. In the present invention, the ratio of spacing gaps on the 20 peripheral surface of the draft tube is adjusted to a range such that both of the circulation of the solution contained in the tank in and out of the draft tube using the peripheral surface of the draft tube and the circulation of the solution in and out of the draft tube via the spacing gaps provided at the peripheral 25 surface of the draft tube are obtained. Therefore, the bubble column having such draft tube can achieve the circulation of solution contained in the tank even when the liquid level of the ;, solution contained in the tank varies. Since the structures of the above-mentioned draft tubes are 30 simple, in the case that the draft tube is provided in such a large bubble column that an operator can enter, all of the hollow pipes constituting the draft tube are "arranged in the area to which the operator can reach, the maintenance operation is easier than in the case using the prior draft tufoLe for the bubble column. 35 Herein "the maintenance operation" means the welding and repair of the pinhole in the hollow pipe and a series of coil renewal operation in which the coil is broken down to be taken out of the manhole provided above the bubble column and a new coil is inserted to be welded and connected. 40 Considering the maintenance facility, the .spacing gaps between the hollow pipes constituting the draft tube are preferably a spacing gap such that that the operator" s hand can be inserted therein. Specifically, the spacing gap is preferably larger than the thickness (for example larger than 2cm) of the fingers of the 5 operator (generally adult) and more preferably larger than the thickness between the flat and back ofrthe operator"s hand (for texample larger than 4cm). r& However, if the draft tube of the present invention is used for a small bubble column which has a difficulty for the operator 10 to enter the tank of the bubble column and to operate therein, the spacing gap is not Limited to the above. The present invention also relates to the bubble column which is provided with the draft tube described above in a tank for containing!solution. 15 The draft tube described above is provided in the tank of the bubble column, so that the bubble column is effectively operated irrespective of the liquid level of the solution. When the bubble column is used for cultivation of microorganisms, the medium for cultivation contained, in the tank 20 is controlled to be a suitable temperature for cultivation, of microorganisms by circulating a heat exchanging medium in the draft tube. Further, when the bubble column is used for gas absorbing operation, even if the reaction heat generated when gas is absorbed in the gas absorbing solution is heat generation 25 or heat absorption, the gas absorbing Solution contained in the tank can be controlled to be a desired temperature. The description of operation and effect based on individual draft tube of the present invention are-omitted here because the operation and effect in case where theidraft tube of the present 30 invention is used for the bubble column are described above. The present invention also relates to a bubble column in which plural draft tubes in the bubble coluitin as described above are provided in concentric or substantially in concentric, In this specification, the term "substantially jn 35 concentric" means that it is not necessary to be a coisplcite concentric nor to have the same center. Since the bubble column is constructed such that the plaza draft tubes as described above are provided in concentric or substantially in concentric, the bubble column can be effectively 40 operated irrespective of the liquid level of the solution. Further, the solution contained in the bubble column is effectively kept at a desired temperature by circulating a heat exchanging medium in each one of the plural draft tubes. Further it is able to keep large heat transferring area per a unit volume. The present invention also relates to a bubble column, in 5 which the draft tube occupies 10 to 90 percent of sectional area of the tank for containing solution therein in the1 bubble column. When plural draft tubes are provided concentrically or substantially concentrically, "the sectional area of the draft tube" means the sectional area of the most outer draft tube. 10 In the bubble column, the solution contained in, the tank is effectively circulated in and out of the draft tube provided in the tank, and the solution contained in the tank is effectively kept at a desired temperature when a heat exchanging medium is circulated in the draft tube. Therefore, for cultivation of a 15 microorganisms, effective culture can be conducted at optimum conditions. Further, for gas absorption operation, effective gas exchange operation can be conducted. The present invention also relates to the bubble column in which a sparger is provided at the position lower" than the draft 20 tube in the tank. In the bubble column of this type, when the sparger is provided in the area of the draft tube, many bubbles are supplied into the solution contained in the draft 1 tube comparing with the solution existing between the outside bf the draft tube and the 25 tank because the sparger is provided below the draft tube in the bubble column described above. Therefore, the solution contained in the draft tube causes a liquid flow from bottom to up in the tank, and the solution contained between the outside of the draft tube and the tank causes a liquid flow from top to 30 bottom in the tank. Hereby, the circulation of the solution in the tank is generated in and out of the draft tube using the peripheral surface of the draft tube. In additidn, circulation in and out of the draft tube is generated via the spacing gaps provided for the peripheral surface of the draft tube. 35 In contrast, if the sparger is provided outside of the draft tube area in the tank, many bubbles are supplied into the solution existing between the outside of the "ciraft tube and the tank comparing with the solution in the draft tube area. Therefore, i the solution existing between the outside of the draft tube and 40 [the tank causes a liquid flow from bottom to top in the tank and the solution existing in the draft tube causes a liquid flow from top to bottom in the tank. Thus, the circulation in and out of the draft tube is generated in the solution in the tank using the peripheral surface of the draft tube. In addition, the circulation in and out of the draft tube is generated via the 5 spacing gaps provided for the peripheral surface of the draft tube. In the bubble column, two circulations, namely, circulation using the peripheral surface of the draft tube and the circulation using the spacing gaps provided for the side circumference of 10 the draft tube,.can be generated in the solution contained in the tank according to the above-mentioned bubble column. Therefore, if the liquid level of the solution contained in the tank varies in what way, the solution in the tank can be agitated. The sparger may be provided so that bubbles are supplied 15 inside and outside of the draft tube simultaneously. In this case, although the circulation flow in the bubble column becomes irregular, the contact efficiency of;the bubbles is improved. The present invention also relates to a bubble column in which the sparger is provided inside the draft tube when the tank for 20 containing solution therein is shown in plan view. Here " the sparger is provided inside the drafi~ tube when the tank for containing solution is shown in plan view" means (that the installation position of the sparger may be located anywhere inside the most outer draft tube, namely not only inside 25 the most inner draft tube but in the area between the most inner draft tube and the most outer draft in case that plural draft tubes of the present invention are provided concentrically or substantially concentrically and the tank for containing the solution therein is shown in plan view. 30 The vertical position (height) where the sparger is provided may be any position, so long as it ist-lower than the upper end of the draft tube. When a solution is contained in the"ffcank of the bubble column, lots of bubbles are supplied into the-solution existing in the 35 draft tube from the sparger comparing With the solution existing between the outside of the draft tube and the tank. Therefore, the solution inside the draft tube causes an upward liquid flow and the solution between the outsideTof the draft tube and the tank causes a downward liquid flow. Thereby, circulation in the i 40 solution contained in the tank is generated in and out of the draft tube using the peripheral surface of the draft tube. In addition, the circulation in and out of the draft tube is generated via the spacing gaps provided for the peripheral surface of the draft tube. Two circulations mentioned above can be generated in the 5 solution contained in the tank according to the above-mentioned bubble column. Therefore, if the liquid level of the solution contained in the tank varies in what way, the solution in the tank can be agitated. The present invention relates to a bubble column in which 10 the sparger is provided out of the area of the draft tube when the tank for containing solution therein is shown in plan view. Here, " the sparger is provided out of the area of the draft tube when the tank for containing solution therein is shown in plan view" means that the installation position of the sparger 15 is outside the most outer draft tube when plural draft tubes of the present invention are provided concentrically or substantially concentrically and the tank for containing the solution therein is shown in plan view. The vertical position (height) where the sparger is provided 20 may be any position, so long as it is lower than the upper end of the draft tube. Lots of bubbles are supplied into the solution existing between the outside of the draft tube and the tank from the sparger comparing with the solution existing inside the draft tube. 25 Therefore, the solution between the outside of the draft tube and the tank causes an upward liquid flow and the solution in the draft tube causes a downward liquid flow. Thereby, circulation in the solution contained in the tank is generated in and out of the draft tube using the peripheral 30 surf ace, of the draft tube. In addition, the circulation in and out of the draft tube is generated via the spacing gaps provided for the peripheral surface of the draft tube. Two circulations mentioned above can be generated in the 35 solution contained in the tank according to the above-mentioned bubble column. Therefore, if the liquid level of the solution contained in the tank varies in what way, the solution in the tank can be agitated. 40 BRIEF DESCRIPTION OF THE DRAWINGS Fig. 1 is a partially cut away perspective view schematically showing one embodiment of the bubble column of the present invention. Fig.2 is a sectional view schematically showing the bubble column in Fig.l. 5 Fig.3 is a schematic cross section seen from top to down when the bubble column in Fig.l is cut along the line III - III in Fig.1. Fig.4 is an enlarged diagram of a part of the draft tube used in Fig.l, Fig.4a is a perspective view diagrammatically showing 10 the condition before one hollow pipe is connected to another hollow pipe, both pipes constituting the draft tube 3, when the draft tube is constructed, and Fig.4b is a perspective view diagrammatically showing the condition after one hollow pipe is connected to another hollow pipe, both pipes constituting the 15 draft tube, when the draft tube is constructed. Fig. 5 is a partially cut away perspective view schematically showing other embodiment of the bubble column of the present invention. Fig.6 is a sectional view schematically showing the bubble 20 column in Fig.5. :! , Fig .7 is a partially cut away perspective view schematically showing other embodiment of the bubble3 column of the present i invention. " Fig.8 is an enlarged diagram of a part of the draft tube used 25 in Fig.7, Fig.8a is a perspective view diagrammatically showing the condition before one hollow pipe is connected to another hollow pipe, both pipes constituting the draft tube, when the draft tube is constructed, and Fig.8b is a perspective view diagrammatically showing the condition after one hollow pipe is 30 connected to another hollow pipe, both pipes constituting the draft tube, when the draft tube is constructed. Fig.9 is a partially cut away perspective view schematically showing other embodiment of the bubble column of the present invention. 35 Fig .10 is a partially cut away perspective view schematically showing other embodiment of the bubble column of the present invention. Fig. 11 is a sectional view schematically showing the bubble column in Fig.10. v"i ■: 40 Fig.12 is a schematic cross section seen from top to down when the bubble column in Fig.10 is cut along the line XVII - XVII in Fig.10. Fig. 13 is a partially cut away perspective view schematically showing other embodiment of the bubble column of the present invention. Fig. 14 is a sectional view schematically showing the bubble column in Fig.13. Fig. 15 is a partially cut away perspective view schematically showing other embodiment of the bubble column of the present invention. Fig. 16 is a partially cut away perspective view schematically showing other embodiment of the bubble column of the present invention. Fig.17 shows an experimental data for confirming the performance of the bubble column of the:present invention in which the correlation of the oxygen absorption speed per a unit volume to the solution contained in the tank and the change in the solution volume contained in the tank: is shown. The horizontal axis shows the superficial gas velocity Ug [m/second] and the vertical axis shows the oxygen absorption speed per a unit volume [kgmol - 02/m3/hour] into sodium sulfite solution including copper sulfate. v Each mark, namely a zigzag bar, a black square, a black triangle and a black circle, shows the result when the liquid volume is 0.6KL, 0.7KL, 1.0KL and 1.2KL respectively. Fig. 18 is a partially cut away perspective view schematically showing other embodiment of the bubble column of the present invention. Fig. 19 is a sectional view schematically showing the bubble column in Fig.18. Fig.20 is a schematic cross section, seen from top to down when the bubble column in Fig.18 is cut along the line XX - xx in Fig.18. Fig.21 shows a perspective view schematically showing one embodiment of the prior bubble column. Fig.22 shows a perspective view schematically snowing other embodiment of the prior bubble column. Fig.23 shows a perspective view schematically showing other embodiment of the prior bubble column. Fig.24 shows a view schematically showing other embodiment of the prior bubble column. BEST MODE FOR CARRYING OUT THE INVENTION Preferred embodiments of a draft tube1, a sparger and a bubble column provided with them are explained below referring to the attached drawings-5 [Embodiment of the Present Invention 1-4] In the embodiments 1 - 4, an example provided with one draft tube in a tank is explained. 10 [Embodiment of the Present Invention 1] Fig. 1 is a partially cut away perspective view schematically showing one embodiment of the bubble column of the "present invention. 1 Fig.2 is a sectional view schematically showing the bubble column in Fig.l. Fig. 3 is a schematic cross section seen from top to down when the bubble column in Fig.l is cut along the line III - III in Fig.l. As shown in Fig.l, the bubble column 1 has a tank 2 for 20 containing a medium for cultivation and gas absorbing solution, a draft tube 3 provided in the tank 2 and a sparger 4, which is provided below the draft tube 3 in the Bank (can)" 2. The reference numeral 2a in Fig.1 indicates a cover of the tank (can) 2, and 2h indicates a vent hole provided for the cover 25 2a if necessary. The member indicated with 6 is a discharge pipe and the member indicated with 5 is a pillar for installing the draft tube 3 in the tank 2. $ if." The bubble column 1 uses a draft tube comprises a hollow pipe and has spacing gap S3 in whole peripheral thereof as the draft 30 tube 3. Specifically, the draft tube 3 comprises a hollow pipe which is wound spirally like a coil. The material of the hollow pipe constituting the draft tube 3 is not particularly limited, so long as it is the material 35 generally used for the draft tube attached to a bubble column. For example, it may be metal, plastic and so on. When the bubble column 1 is used for cultivation of microorganisms, the tank 2 is steamed £q£ sterilization before culturing. 40 Therefore, considering steaming, the^material of the hollow pipe constituting the draft tube 3 is preferably such a material 13 aa durable for ateaminy. Accordingly, t;he materia L is preferably metal. . As metal, any metals which, are generally used may be used, for example, stainless steel, aluminum, titanium and so on, and 5 stainless steel is preferably used. , In the case wherein the bubble column is not subjected to high temperature such as steaming, for example the bubble column 1 is used for gas exchange and the tank 2, the material of the hollow pipe constituting the draft tube 3 may be resin. 10 The diameter of the hollow pipe of the draft tube 3 is freely selected depending on the intended purpose and size of the bubble column 1. It is usually limited to 5 to 200mm, preferably 50 to 100mm. The cross sectional shape of the draft tube 3 is usually circle, 15 however, it is not limited to circle and it may be oval, triangle or polygon like rectangle if the tube is functioned as a draft tube. The draft tube is constructed so that spacing gaps are formed between the hollow pipes. 20 The spacing gaps between the hollow pipes are not required to be uniform all over the draft tube,; so long as the solution in and out of the draft tube is circulated each other when the hollow pipes are used for a draft tube. The spacing gaps between the hollow pipes are not 25 specifically limited, however, it is advantageous that the spacing gap is formed so as to facilitate maintenance in case that the bubble column is used as a production installation. Except for the bubble column with 5 to 1000 litters used for research in an experimental laboratory, the spacing gap is 30 preferably over 2cm so that the hands of the operator are inserted. If the ratio of spacing gaps of the draft tube 3 is too large, free circulation of the solution in and out of the draft tube is improved, however, the effect of the draft tube 3 such as mixing performance is reduced or the surface area (heat transfer area) 35 of the hollow pipe constituting the draft tube 3 also serving as a heat exchanger is reduced as mentioned later. On the contrary, if the ratio of spacing gaps of the peripheral surface of the draft tube 3 is too small, the peripheral surface j(heat transfer area) of the hollow pipe is increased, but the 40 free circulation of the solution is deteriorated. Considering the above, the ratio of"spacing gaps of the draft tube 3 is limited to 1 to 99% for the peripheral of the draft tube, preferably 10 to 90%, more preferably 25 to 50%. Because of the spacing gaps in the peripheral surface of the draft tube 3, when the draft tube 3 is installed in the tank 2, 5 the solution is capable of circulation in and out of the draft tube 3 when the liquid level of the solution contained in the tank is in any level. A heat exchanging medium is able to be circulated in the hollow pipe wound spirally like a coil and constituting the draft tube 10 3, so that the draft tube 3 may be functioned as a heat exchanger. In this embodiment, the heat exchanging medium is circulated from one end 3a to the other end 3b of the draft tube 3, however, the heat exchanging medium may be circulated from the other end 3b to one end 3a. 15 If the solution contained in the bubble column 1 generates heat when the bubble column 1 is operated, a cooling medium is circulated in the draft tube 3. If the)"solution contained in the bubble column 1 absorbs heat when the bubble column 1 is operated, a heating medium is circulated in the draft tube 3. The heat 20 exchanging medium is preferably water| however, a medium other than water may be used, so long as it is usually used as a heat exchanging medium. Construction of the draft tube 3 used for the bubble column 1 is explained, hereinafter. 25 Fig4 is an enlarged diagram of a part of the draft tube 3 used for the bubble column 1. Fig.4a is a perspective view diagrammatically showing the condition before one hollow pipe is connected to another hollow pipe, both pipes constituting the draft tube 3, when the draft tube 3 is constructed. Fig.4b is 30 a perspective view diagrammatically showing the condition after one hollow pipe is connected to another hollow pipe, both pipes constituting the draft tube 3, when the draft tube is constructed. The hollow pipe constituting the draft tube 3 of the bubble column 1 may be an integrally molded She. If the dr,aft tube 3 35 is large, an integrally molded draft tube 3 is hardly produced. According to the bubble column 1, as shown in Fig. 4, hollow bipes p3 ... constituting the draft tube 3 are connected by welding "each other. Further, if the spacing gaps between the hollow pipes 40 constituting the draft tube 3 of the bubble column 1 are set so as to be inserted with hands and fingers (specifically, the spacing gap like the thickness of the hands and fingers of operators (usually adult) (for example over 2cm) and more preferably the thickness between the flat and back of operator * s hand (for example larger than 4cm)), it becomes easier to repair 5 pinhole in any one of the hollow pipes constituting the draft tube 3. Next, construction of the sparger 4 is explained. The bubble column 1 uses the sparger 4 having a trunk pipe 4a and plural branch pipes 4b-,, provided so as to be branched 10 off from the trunk pipe 4a. In Fig.l, "4c" shows a gas supply- port. Plural penetrating apertures are provided at each upper part of the trunk pipe 4a and plural branch pipes 4b When the tank 2 for containing the.solution therein in the 15 bubble column 1 is seen from above, the: trunk pipe 4a and plural branch pipes 4b- constituting the sparger 4 are provided within the area of the draft tube 3. Next, usage and operation of the bubble column 1 are explained. 20 For cultivation of microorganisms with the bubble column 1, microorganisms and a medium for cultivation are put in the tank 2, and gas such as air is supplied into the tank 2 from the sparger 4. In case that the solution contained in the tank 2 is 25 excessively heated above the temperature suitable for cultivation of microorganisms by fermentation heat generated .* during culturing microorganisms, a cooling medium such as a cooling water is circulated in the hollow pipe wound spirally like a coil and constituting the draft tube 3: to adjust the 30 temperature of solution contained in" the tank 2 so as to be suitable for cultivation of microorganisms. On the other hand, in case that the temperature of solution contained in the tank 2 is lower than that suitable for cultivation of microorganisms during culturing microorganisms, a heating 35 medium such as a heated water is circulated in the hollow pipe wound spirally like a coil and constituting the draft tube 3 to adjust the temperature of solution contained in the tank 2 so as to be suitable for cultivation of microorganisms. For gas absorbing operation with the bubble column 1, a gas 40 absorbing solution for absorbing an objective gas is put in the tank 2, and the gas including the gas to be absofbed in the gas absorbing solution contained in the tank 2 is supplied from the sparger 4. In the case that a certain component in the gas supplied to the gas absorbing solution contained in the tank 2 from the sparger 5 4 is absorbed in the gas absorbing solution, when heat is absorbed, a heating medium such as a heated water is circulated in the hollow pipe wound spirally like a coil and constituting the draft tube 3, and on the other hand, when heat is generated, a cooling medium such as a cooling water is circulated in the hollow pipe wound 10 spirally like a coil and constituting the1 draft tube 3 for cooling the gas absorbing solution contained in the tank 2. According to the bubble column 1, the draft tube 3 provided in the tank 2 comprises the hollow pipe" is wound spirally like a coil, and therefore, when the solution is contained in the tank 15 2, the contained solution in the tank 2 is circulated in and out of the draft tube 3 through the spacing gaps of the hollow pipe wound spirally like a coil. , By using the bubble column 1, cultivation of microorganisms and gas absorption can be executed irrespective of the liquid 20 level of the solution contained in the" tank 2. !" Thus in the bubble column 1, the draft tube 3 comprised of the hollow pipe wound spirally like a coil is provided in the tank 2, and a heat exchanging medium (a coaling medium or a heating medium) is circulated in the hollow pipSIconstituting the draft 25 tube 3, thereby effectively keeping trie: solution* contained in the tank 2 at a suitable temperature. In addition, all of the external! peripheral surface or substantially all of the external peripheral surface of the hollow pipe constituting the draft tube 3 comes into contact with 30 the solution in the tank 2, thereby obtaining a large heat transfer area. Therefore, the draft tube 3 is excellent in heat exchanging ability between the heat exchanging medium and the solution contained in the tank 2 when the heat exchanging medium (a cooling medium or a heating medium) is circulated. 35 Further, in this embodiment, a blow nozzle of the sparger . 4 is provided within the area of the draft tube 3 when the draft tube 3 is seen from above (see Fig.3), and when gas such as air is supplied into the tank 2 from the sparger 4, many bubbles are uniformly supplied into the solution existing in the draft tube 40 3 comparing with the solution existing; between the outside of ; the draft tube 3 and the tank 2 when the draft tube 3 is shown in plan view. , Apparent density of solution in the draft tube 3 becomes smaller than that of solution between the outside of the draft tube 3 and the tank 2, and the liquid flow directing from the 5 bottom to the top in the tank 2 is generated in the solution in the draft tube 3. As for the solution between outside of the draft tube 3 and the tank 2, the downward liquid flow in the tank 2 is generated. Other than the above-mentioned flow perpendicular along the 10 tank 2, a horizontal liquid flow is generated such that the solution including bubbles is moved from the inside of the draft tube 3 to the outside of the draft tube 3 through the spacing gaps between the hollow pipe constituting the draft tube 3 in the bubble column 1. The solution flow created by a harmonious 15 combination of the perpendicular flow and the horizontal flow is generated, so that the contained solution is well mixed comparing with the prior bubble column 301 in which a tubular draft tube 303 is provided in the tank 202 as shown in Fig.21. As a result, cultivation of microorganisms is expedited with 20 thebubble column 1 and the supply performance of oxygen into the solution contained in the tank 2 is improved comparing with the conventional bubble column 301 having the tank 202 in the tubular draft tube 303. i As mentioned above, the bubble column has a simple structure 25 ard acquires a large heat transfer area^bf the draft tube 3 as a heat exchanger and therefore, is preferably used ats a scaled-up large or high bubble column. [Embodiment of the Present Invention 2.) 30 Fig.5 is a partially cut away perspective view schematically showing other embodiment of the bubble^ column of the present invention. Fig.6 is a sectional view schematically showing the bubble column in Fig.5. 35 The bubble column 21 is the same as the bubble column 1 shown in Fig. 1 other than the following constructions, and accordingly, the same members of the bubble column 21 as those of the bubble column 1 are given the same reference numerals, and their explanations are omitted here. 40 Construction of the draft tube is different between the bubble column 21 and the bubble column 1, and other constructions thereof are the same. Therefore, the construction of the draft tube used for the bubble column 21 is mainly explained hereinafter. The bubble column 21 uses a draft tube 23 in which plural draft tube units 23U1, 23u2, 23U3 wound like a coil are vertically 5 stacked up in the tank 2. The construction of each one of the draft tube units 23U1, 23U2, 23U3 is the same as that of the draft tube 3 applied to the bubble column 1 shown in Fig.l. In the bubble column 21, a heat exchanging medium is 10 circulated in each one of the draft tube units 23U1, 23U2, 23U3 wound like a coil. More specifically, the heat exchanging medium is supplied from the heat exchanging medium supply port 3a provided at the lower part of each one of the draft tube units 23U1, 23U2, 23U3 15 and is discharged from the heat exchanging medium discharge port 3b provided at the upper part of each one of the draft tube units 23U1, 23U2, 23U3. The draft tube units 23U1, 23U2, 23U3 wound like a coil are vertically stacked up in the tank 2 in the bubble column 21, and 20 a heat exchanging medium is circulated though each of the draft tube units 2301, 23U2, 23U3. Therefore;the bubble column 21 of the present embodiment is more advantageous in that temperature irregularity is hardly caused in the solution in the tank 2 than the bubble column 1 in which only one draft tube 3 is provided 25 in the tank 2 and a heat exchanging medium is supplied from the heat exchanging medium supply port 3a provided at the lower part of the draft tube 3 and is discharged from the heat exchanging medium discharge port 3b provided at the upper part of the draft tube 3,. 30 The bubble column 21 is the same as the bubble column 1 other than that the constructions of the draft tube 23 of the bubble column 21 and the draft tube 3 of the bubble column 1 are different as mentioned above, and the operation and effect bf the bubble column 21 are the same as those of the bubble column 1 other than 35 the mentioned above. Accordingly, among the operations and the effects of the bubble column 21, the same operations and effects as that of the bubble column 1 are omitted here. The bubble column 21, like the bubble"column 1, is preferably used as a scaled-up large or high bubble column." 40 tEmbodiment of the Present Invention 3] "■ I - Fig.7 is a partially cut away perspective view schematically showing other embodiment of the bubble column of the present nvention. Since the bubble column 41 is the same as the bubble column 5 1 shown in Fig.l except that the construction of the draft tube 43 is different from the construction of the draft tube 3, and accordingly, the same members of the bubble column 41 as those of the bubble column 1 are given the same reference numerals, their explanations are omitted here. 10 The bubble column 41 uses the draft tube 43 comprised of a hollow pipe which is bent in zigzag at its up and down for the tank 2, and a heat exchanging medium is supplied if necessary. In the bubble column 41, such a zigzag hollow pipe is used as the draft tube 43 provided in the tank 2, so that the solution 15 in the tank 2 is circulated in and out of the draft tube via the spacing gaps between the hollow pipe which is bent in zigzag when the solution is put in the tank 2. Accordingly, cultivation of microorganisms and gas absorption can be conducted in the bubble column 41 even if the ■ . . "f * 20 liquid level of the solution in the tank 2 is at any level. Like the above-mentioned bubble cofumns 1 and" 21, the ratio of spacing gaps of the draft tube 43 comprised of the hollow pipe bent in zigzag is limited to 1 to 99% for the entire peripheral surface of the draft tube 3, preferably 10 to 90%, more preferably 25 20 to 50%." Since the operation and effect of "the bubble column 41 are the same as those of the bubble column 1 mentioned in the Embodiment 1, their explanations are omitted here. Fig.8 is an enlarged diagram of a part of the draft tube 43 30 used in the bubble column 41: Fig.8a is a perspective view diagrammatically showing the condition before one hollow pipe is connected to another hollow pipe, both pipes constituting the draft tube 43, when the draft tube 43 is constructed; and Fig.8b is a perspective view diagrammatically showing the condition 35 after one hollow pipe is connected to another hollow pipe, both pipes constituting the draft tube 43, when the draft tube 43 is constructed. The hollow pipe constituting the draft tube 43 used in the bubble column 41 may be an integratedfolded one, however, if 40 the draft tube 43 is large, production"of the draft tube as an integrated molded tube is difficult, In such a case, plural hollow pipes p43 are preferably connected by welding. Further, if at least one part of each one of the hollow pipes p43 is designed to be fixed to the pillar 5 by welding, when the 5 hollow pipe to be exchanged is removed from the hollow pipes p43 constituting the draft tube 3, the remaining member of the draft tube 43 is not broken because the remaining member is secured to the pillar 5. Therefore, only the hollow pipe to be exchanged is easily removed from the draft tube 43 and a new hollow pipe 10 is easily attached to the removed part, thereby achieving advantage that maintenance of the bubble column 41 is completed with simple operation. Further, if the spacing gap between the hollow pipes constituting the draft tube 43 of the bubble column 41 are set 15 so as to be inserted with hands and fingers (specifically, the spacing gap like the thickness of hands and fingers of operators (usually aduit) (for example over 2cm) and more preferably the thickness between the flat and back of the operator" s hand (for example larger than 4cm)), when pinhole is caused in any one of 20 the hollow pipes constituting the draft tube 43, repair of the pinhole is facilitated. [Embodiment of the Present Invention"4] Fig. 9 is a partially cut away perspective view schematically 25 showing other embodiment of the bubble column of the present invention. :\ ! The bubble column 61 is the same as the bubble column 21 shown in Fig.5 other than the following constructions, arid accordingly, the same members of the bubble column 61 as those of the bubble 30 column 21 are assigned the same reference numerals, and their explanations are omitted here. In the bubble column 61, instead of the draft tube 23 used in the bubble column 21, the draft tube 43 used in the bubble column 41 shown in Fig.7 is used as plural draft tube units 63U1, 35 63U2, 63U3, which are vertically stacked up in the tank. A heat exchanging medium is circulated in each one of the draft tube units if necessary. " The bubble column 61 has the same effect as the bubble column 1 and the bubble column 41. In the bubble column 61, the draft 40 tube units 63U1, 63U2, 63U3 are vertically stacked up in the tank 2, and a heat exchanging medium is circulated through each of the draft tube units 63U1, 63U2, 63U3. Therefore, the bubble column 61 of this embodiment is more advantageous in that temperature irregularity is hardly caused in the solution in the tank 2 than the bubble column 1 or 41 in which only one draft 5 tube 3 or 43 is provided in the tank 2, and a heat exchanging medium is supplied from the heat exchanging medium supply port 3a provided at the lower part of the draft tube 3 or 43 and is discharged from the heat exchanging medium discharge port 3b provided at the upper part of the draft tube 3 or 43,. 10 Specifically, the bubble column 61 is preferably used as a scaled-up large or high bubble column. [Embodiment of the Present Invention 5 to 8] In the embodiments of the present invention 5 to 8, an example 15 provided with two draft tubes in a tank is explained. [Embodiment of the Present Invention 5] Fig. 10 is a partially cut away perspective view schematically showing other embodiment of the bubble column of the present 20 invention. Fig. 11 is a sectional view schematically showing the bubble column in Fig.10. " Fig.12 is a schematic cross section when seen from top to bottom when the bubble column in Fig.10 is cut along the line 25 XyTI - XVII in Fig.11. The bubble column 71 is the same as the bubble column 1 shown in Fig. 1 other than the following constructions, and accordingly the same members of the bubble column 71 as those of the bubble column 1 are given the same reference numerals, and their 30 explanations are omitted here. ,, The bubble column 71 is different from the bubble column 1 in that two draft tubes 3A and 3B whichfare formed by spirally winding a hollow pipe like a coil are"provided. Two draft tubes 3A, 3B are provided in concentric or in 35 substantially concentric. A heat exchanging medium such as a cooling medium or a heating medium is circulated in the draft tubes 3A, 3B. The sparger 4 supplies bubbles in two draft tubes 3A, 3B, namely in the inner draft tube 3B. 40 Usage and operation of the bubble column 71 are almost the same as those of the bubble column 1, and accordingly, their explanations are omitted here. However, because two draft tubes 3A, 3B are provided in the bubble column 71, the temperature of solution contained in the tank 2 is more accurately controlled to be a desired temperature comparing with the bubble column 1. 5 winding directions of the draft tubes 3A, 3B may be the same or may be different when they are seen from top to bottom. [Embodiment of the Present Invention 6) Fig. 13 is a partially cut away perspective view schematically 10 showing other embodiment of the bubble column of the present invention. Fig. 14 is a sectional view schematically showing the bubble column in Fig. 13. The bubble column 81 is the same as the bubble column 21 shown 15 in Fig.5 other than the following constructions, and accordingly the same members of the bubble column 81 as those of the bubble column 21 are given the same reference numerals, and their explanations are omitted here. The bubble column 81 is different from the bubble column 21 20 in ^hat six draft tube units 23AU1, 23AU2, 23AU3, 23BU1, 23BU2, 23BU3 formed by spirally winding a hollow pipe like a coil are provided. The draft tube units 23AU1, 23AU2, 23AU3 among six draft tube units 23AU1, 23AU2, 23AU3, 23BU1, 23BU2, 23BU3 are stacked up 25 vertically to constitute a draft tube 23A, and the draft tube units 23BU1, 23BU2, 23BU3 are vertically stacked up inside of the draft tube 23A to constitute a draft tube 23B. The draft tubes 23A and 23B are provided in concentric or substantially in concentric. > 30 Like the bubble column 21, a heat exchanging medium is circulated in each one of the draft tube&23A, 23B,Uf necessary. The sparger 4 supplies bubbles in the inner diraft tube 23B among two draft tubes 23A, 23B. Usage and operation of the bubble column 81 are almost the 35 same as those of the bubble column 21,; and accordingly, their explanations are omitted here. However^ because two draft tubes 23A, 23B are provided in the bubble column 81, the temperature of solution contained in the tank 2 is more accurately controlled to be a desired temperature comparing with the bubble column 21. 40 Winding directions of the draft tubes 23A, 23B may be the same or may be different when they are seen from top to bottom. [Embodiment of the Present invention 7] Fig. 15 is a partially cut away perspective view schematically showing other embodiment of the bubble column of the present 5 invention. The bubble column 91 is the same as the bubble column 41 shown in Fig. 7 other than the following constructions, and accordingly, the same members of the bubble column 91 as those of the bubble column 41 are given the same reference numerals, and their 10 explanations are omitted here. The bubble column 91 is different from the bubble column 41 in that two draft tubes 43A, 43B which are formed with hollow pipes bent in zigzag up and down are provided. Two draft tubes 43A, 43B are provided in concentric or in 15 substantially concentric. A heat exchanging medium such as a cooling medium or a heating medium is circulated in each draft tube. The sparger 4 supplies bubbles in two draft tubes 43A, 43B, namely in the inner draft tube 43B. 20 \Usage and operation of the bubble column 91 are almost the same as the bubble column 41, and accordingly, their explanations are omitted here. However, because two"draft tubes 43A, 43B are provided in the bubble column 91, the temperature of solution contained in the tank 2 is more accurately controlled to be a 25 desired temperature comparing with the bubble column 41. [Embodiment of the Present Invention 8] Fig. 16 is a partially cut away perspective view schematically showing other embodiment of the bubble column of the present 30 invention. The bubble column 101 is the same as the bubble column 61 shown in Fig.9 other than the following constructions, and accordingly, the same members of the bubble column 101 as those of the bubble column 61 are given the slime reference numerals, 35 and their explanations are omitted here. The bubble column 101 is different" from the bubble column 61 in that six draft tube units 63AU1, 63AU2, 63AU3, 63BU1, 63BU2, 63BU3 formed by bending a hollow pipe in zigzag are provided. The draft tube units 63AU1, 63AU2, 63AU3 among six draft tube 40 units 63AU1, 63AU2, 63AU3, 63BU1, 63BI&, 63BU3 are stacked up vertically to constitute a draft tube 63A, and the draft tube units 63BU1, 63BU2, 63BU3 are vertically stacked up inside of the draft tube 63A to constitute a draft tube 63B. The draft tubes 63A and 63B are provided in concentric or substantially in concentric. A heat exchanging medium is 5 circulated in each one of the draft tubes 63A, 63B, if necessary. The sparger 4 supplies bubbles in ±.he inner draft tube 63B among two draft tubes 63A, 63B. Usage and operation of the bubble rcolumn 101 are almost the same as the bubble column 61, and accordingly their explanations 10 are omitted here. However, because two draft tubes 63A, 63B are provided in the bubble column 101, the temperature of solution contained in the tank 2 is more accurately controlled to be a desired temperature comparing with the bubble column 61. 15 Next,, the present invention is explained based on the experimental data. [Experimental Example 1] In this experiment, the bubble column 1 shown in Fig.l was used, and sodium sulfite (Na2S03) solution including copper 20 sulfate was put in the tank 2, gas with a predetermined oxygen concentration was supplied from the sparger 4 to the sodium sulfite solution including copper sulfate contained in the tank 2, and the oxygen concentration included in the gas discharged from the tank 2 was measured, and the oxygen concentration 25 absorbed per a unit volume of the "sodium sulfite solution including copper sulfate was calculated. In this experiment, a tubular tower having the inner diameter of 1000mm and the height of 2395mm was used as1the tank 2. Also, a pipe 3/8B (external diameter = 17.3mm) was used as 30 a hollow pipe constituting the draft tube 3. , Also used in this experiment was the draft tube 3 formed by spirally winding the above-mentioned hollow pipe (pipe 3/8B) (external diameter ~ 17.3mm) like a coil. The inner diameter of the draft tube 3 was 715mm and its height 35 was 1430mm. The spacing gap between each hollow pipe constituting the draft tube 3 was 10.2mm, and the ratio of spacing gaps of peripheral surface of the draft tube 3 was 37%. Thus constructed draft tube 3 was provided in the tank 2 so 40 that the lower end of the draft tube 3 was 205mm above the bottom of the tank 2. At first a predetermined amount of sodium sulfite solution 5 including copper sulfate.mentioned above was putted in the tank 2 of the bubble column 1. Next, gas with a predetermined oxygen concentration was supplied from the sparger 4 to the sodium sulfite solution including copper sulfate contained in the tank 2. 10 The oxygen concentration of supplied gas was made constant, and the ventilation amount of gas was changed. Measurement was carried out for each case that the solution amount was 0.6KL, 0.7KL, 1.0KL, and 1.2KL. The distance from the bottom to the liquid surface (liquid depth) was 760mm when the solution volume 15 was 0.6 KL, 1020mm for 0.7KL, 1280mm for 1.0KL, and 1550mm for 1. 2KL. In any cases, the liquid surface existed between the upper end and the lower end of the draft tube. The concentration of oxygen in the gas discharged from the tank 2 was measured for each case, the difference between the 20 concentration of oxygen in the supplied gas and the concentration of oxygen in the discharged gas was obtained, and the speed of oxygen absorption per a unit volume of the solution was calculated by the obtained difference. The results of the speed of oxygen absorption at each volume 25 amount versus the speed of ventilation are shown in Fig.17. In Fig. 17, the horizontal axis indicates the superficial gas velocity Ug[m/sec], and the vertical axis indicates the speed of oxygen absorption [kgmol-02/m3/hour]" per a unit volume into the sodium sulfite solution including-Copper sulfate. 30 Each mark, namely a zigzag bar, a black square, a black triangle and a black circle in Fig.17,;shows the: results when the solution volume is 0.6KL, 0.7KL, 1.0KL! and 1.2KL, respectively. When the ventilated solution volume was 1. 2KL, the surface of the solution exceeded the upper end of the draft tube. 35 Even when the solution volume was 1.0KL, the surface of the solution also exceeded the upper end of the draft tube, when the superficial gas velocity was 0.08/sec or O.lOm/sec. As understood from the results in"Fig.17, according to the bubble column 1 of the present invention, when the amount of gas 40 supplied from the sparger 4 into the solution contained in the tank 2 is constant, the speed of oxygen absorption per a unit volume of the solution contained in the tank 2 is kept constant even if the amount of solution contained in the tank. 2 is widely-changed. That is, the bubble column 1 can be used irrespective of the liquid level of the solution. 5 In the Embodiments of the Present Invention 1 - 8, the bubble columns 1, 21, 41, 61, 71, 81, 91, and 101 provided with a sparger 4 are explained, in which the sparger 4 has the trunk pipe 4a and plural branch pipes 4b- • ■ arranged so as to be branched off from the trunk pipe 4a, however they are preferred examples; as 10 a sparger, a sparger, in which air bubble spray nozzles 24b"* are arranged at a predetermined position of a hollow ring body 24a provided in the direction of the center of the draft tubes 3A, 3B like the sparger 24 used for the bubble column 111 shown in Figs. 18, 19, 20, or a sparger, in which plural apertures 304h-* • 15 are formed at the upper surface of the known hollow ring body 304 as shown in Fig.21, can be also used. The Embodiments of the Present Invention 1 to 8 explain the bubble column in which bubbles are supplied from the sparger 4 mainly inside of the draft tube 3, 23, 43, 63, 3A, 23A, 43A, or 20 63A. This is only a preferred examples, and the present invention may use a ring-like sparger which is smaller than the inner diameter of the tank 2 and is larger than the draft tube 3, 23, 43, 63, 3A, 23A, 43A, or 63A (for example, see the sparger 304 shown in Fig.23). The sparger supplies bubbles into the solution 25 contained in the tank 2 to form a flow directing from the bottom to the top in the solution existing between the outside of the ckraft tube 3, 23, 43, 63, 3A, 23A, 43A or 63A and the tank 2, and to form a flow directing from the top,to the bottom in the solution existing inside of the draft tube 3, 23, 43, 63, 3B, 30 23B, 43B, or 63B. Also, a flow directing outside to inside of the draft tube 3, 23, 43, 63, 3A, 23A, 43A, or 63A in the solution in the outside of the draft tube 3, 23, 43, 63, 3A, 23A, 43A, or 63A and the tank 2 via the spacing gaps of the hollow pipe constituting the draft tube 3, 23, 43, 63, (3A, 3B), (23A, 23B), 35 (43A, 43B), or (63A, 63B). Such a sparger may be used for the present invention. Industrial Applicability As mentioned above, according to the1 draft tube of the present 40 invention, the bubble column can be operated irrespective of the liquid level of the solution contained in the tank of the bubble r column, the mixing performance and gas absorption performance of the solution contained in the tank are excellent., the heat. transfer area can be easily obtained, and its maintenance and scale-up can be easily carried out. 5 According to the bubble column of the present invention, the above-mentioned draft tube is used, so that the bubble column can be operated irrespective of the liquid level of the solution contained in the tank of the bubble column, mixing performance and gas absorption performance of the solution contained in the 10 tank are excellent, the heat transfer area can be easily obtained, and its maintenance and scale-up can be easily carried out. WE CLAIM; 1. A draft tube provided in a tank of a bubble tower for containing solution therein, wherein said draft tube comprises of plural stacked tube units, each of which comprises a hallow pipe bent in zigzag and has spacing gaps in the whole peripheral surface of said draft tube and the ratio of said spacing gaps to the area of the whole peripheral surface of said draft tuPe is 1 to 99% and cross sectional shape of said draft tube is circle, oval or polygon. 2. A bubble tower provided with a tank for containing solution therein, wherein the draft tube 0$ claimed in claim lis provided in sad tank and provided with a spargef at position lower than the draft tube according to claim 1. 3. A bubble tower as claimed in claim 2 wherein the plural units of said draft tube as claimed in claim 1 are provided in concentric or substantially in concentric. 4. The bubble tower as claimed in claim 2, wherein said draft tube as claimed in claim locupies 10 to 90 % cross section area of said tanKfor containing solution therein. 5. The bubble tower as claimed in claim 2 wherein said sparger is provided inside the dr#ft tube as claimed in-feewer when said tank is shown in plan view. 29 6. The bubble tower as claimed in claim 2 wherein said sparger is provided outside the draft tub as claimed in claim 1 when said tank is shown in plan view. Dated this 6th day of February, 2004.

Documents:

00092-mumnp-2004-cancelled page(10-8-2004).pdf

00092-mumnp-2004-certificate(10-2-2005).pdf

00092-mumnp-2004-claims(granted)-(10-8-2004).doc

00092-mumnp-2004-claims(granted)-(10-8-2004).pdf

00092-mumnp-2004-correspondence(10-2-2005).pdf

00092-mumnp-2004-correspondence(ipo)-(25-5-2005).pdf

00092-mumnp-2004-drawing(10-8-2004).pdf

00092-mumnp-2004-form 19(6-2-2004).pdf

00092-mumnp-2004-form 1a(10-2-2005).pdf

00092-mumnp-2004-form 2(granted)-(10-8-2004).doc

00092-mumnp-2004-form 2(granted)-(10-8-2004).pdf

00092-mumnp-2004-form 3(6-2-2004).pdf

00092-mumnp-2004-form 5(6-2-2004).pdf

00092-mumnp-2004-power of attorney(6-2-2004).pdf

abstract1.jpg