JP2024074193A - Gas-liquid stirring device - Google Patents

Abstract

To solve a problem that conventional gas-liquid stirring devices consume large amounts of gas-liquid power and stirring power.SOLUTION: A gas-liquid stirring device of the invention comprises: a tank in which a liquid is placed; a circulation pipe which is provided at the tank, introduces the liquid in the tank to the outside of the tank, and returns the liquid into the tank again to circulate the liquid; liquid transfer means which transfers the liquid in the circulation pipe; and ventilation means provided in the circulation pipe. Further, the gas-liquid stirring device includes: a stirring blade provided in the stirring tank and configured to discharge the liquid to the radial outer side; and a stationary blade which is provided at a bottom part of the stirring tank and configured to generate upward flow. An outlet of the circulation pipe is connected to a wall of the tank where circulation flow formed by the stirring blade and the stationary blade occurs to create communication therebetween.SELECTED DRAWING: Figure 1

Description

The present invention relates to a gas-liquid mixing device that has a circulation pipe (circulation line) that removes the liquid in a tank from the tank for cooling or the like and then circulates it back into the tank, and is used, for example, in a bioreactor (biochemical reaction device) for culturing microorganisms or fungi.

Conventionally, microbial bioreactors that mix gas and liquid include mechanical gas-liquid mixing devices that use turbine blades to strongly disperse bubbles, and bubble column type gas-liquid mixing devices that use aeration energy to mix and stir the culture tank using fine bubble release means made of an aeration nozzle that ejects fine bubbles, a ceramic porous body, or a fine bubble membrane.

In addition, for example, when the mixing vessel becomes large-scale, the cooling performance decreases, so it is necessary to install a cooling coil inside the mixing vessel.

As an example of the gas-liquid mixing device for the mechanical bioreactor, as shown in FIG. 4, for example, a rotating shaft 2 is suspended from the center of a cylindrical mixing tank 1 with a bottom containing liquid, and a plurality of mixing blades 3 such as turbine blades are provided at intervals in the vertical direction on the rotating shaft 2, and a baffle 4 extending in the vertical direction is provided on the inner peripheral surface 1b of the mixing tank 1.

Then, there is a mechanical gas-liquid mixing device that provides, for example, an annular vent pipe (sparger ring) 5 under the lowest mixing blade 3, and provides multiple gas outlets (not shown) on the upper surface of the peripheral wall of the annular vent pipe 5, and strongly disperses the gas discharged upward from these gas outlets by the mixing blade 3, thereby aerating the liquid in the mixing tank 1 (Patent Document 1).

In addition, as shown in FIG. 5, a gas-liquid mixing device for a bubble column bioreactor includes a baffle 4 extending in the vertical direction on the inner circumferential surface of a cylindrical stirring tank 1 with a bottom that contains liquid, and a fine bubble discharge means 6 made of an aeration nozzle that discharges fine bubbles, a ceramic porous body, a fine bubble membrane, or the like, at the center of the bottom 1a of the stirring tank 1, and discharges fine bubbles from the bottom 1a to stir the inside of the stirring tank 1 with aeration energy.

For example, when the mixing tank is large-scale (large capacity), the cooling performance decreases, so as shown in Figures 4 and 5, a spiral cooling coil 7 extending vertically along the inner periphery is provided in each mixing tank 1.

JP 2015-116519 A

However, with this cooling method, the denser the cooling coil 7, the worse the fluidity in the mixing tank 1 becomes, lowering the performance of the bioreactor and increasing the mixing and aeration power, posing a problem in terms of energy efficiency.

Therefore, as shown in Figures 6 and 7, there is a cooling method in which both ends of a circulation pipe 8 for circulating liquid are connected in a vertical direction to the outer peripheral wall of the agitation tank 1, a means for cooling the liquid in the circulation pipe 8 (not shown) is provided in the circulation pipe 8, and a pump 9 for transferring liquid is provided. The pump 9 is driven to introduce the liquid in the agitation tank 1 into the circulation pipe 8, and after being cooled by the cooling means, the liquid is returned to the agitation tank 1.

However, the mechanical gas-liquid mixing device still had the drawback of consuming a lot of gas-liquid power and mixing power in order to strongly disperse the gas using the mixing blades 3.

In addition, bubble column bioreactors have capacity (scale) limitations, and due to gas control, flow control, and the effects of the foam layer, their practical use in the 100 to 300 kL (ton) class is extremely low.

In addition, in large reactors of 100 to 300 kL or more, externally cooled mechanical bioreactors with improved heat transfer efficiency are used, but to operate on a scale of 300 kL or more, the stirring power required for gas dispersion is large, which requires unrealistic motor power, and there are issues to be overcome in terms of energy efficiency, making them impractical.

As a result of various experimental studies, the inventors discovered that by using a circulation pipe (circulation line) installed in the mixing vessel for aeration and by utilizing the circulation flow formed by the mixing blades and the stationary blades, it is possible to significantly reduce the mixing power and aeration power and mix the gas and liquid.

To achieve the above object, the gas-liquid mixing device of the present invention is characterized by comprising a tank for holding a liquid, a circulation pipe provided in the tank for introducing the liquid in the tank out of the tank and then circulating it back into the tank, a liquid transfer means for transferring the liquid in the circulation pipe, and a ventilation means provided in the circulation pipe.

The device further includes an agitator blade disposed within the agitation tank for discharging liquid radially outward, and a stator blade disposed at the bottom of the agitation tank for generating an upward flow, and the outlet of the circulation pipe is connected to the wall of the tank where the circulation flow formed by the agitator blade and the stator blade occurs.

The agitating blades are made of multiple flat paddle blades arranged radially in the radial direction, and the stationary blades are made of multiple strips arranged radially, with a gap formed in the center corresponding to the intersection of the strips.

The circulation pipe is also characterized in that the outlet portion is connected to the lower portion of the peripheral side wall of the tank, and the inlet portion is connected to the upper portion.

The ventilation means is also characterized by being formed from a membrane that generates microscopic bubbles.

The inner surface of the mixing vessel is also provided with a baffle extending in the vertical direction.

According to the present invention, the transport force of the circulation pipe is utilized, so the stirring power and aeration power can be reduced and gas-liquid mixing can be achieved.

In addition, a low-power mixing technique is used that uses a circulating flow formed by the mixing blades and stationary blades to mix the liquid, and the fine bubbles are circulated on the circulating flow formed by the mixing blades and stationary blades, so the mixing power and aeration power can be reduced and gas-liquid mixing can be achieved.

FIG. 2 is a longitudinal sectional side view of the gas-liquid mixing device of the present invention. FIG. 2 is an enlarged cross-sectional plan view of the gas-liquid mixing device of the present invention. FIG. 2 is an explanatory vertical cross-sectional side view showing a circulating flow formed in a tank of the gas-liquid mixing device of the present invention. FIG. 1 is a vertical sectional side view of a conventional gas-liquid mixing device. FIG. 11 is a vertical sectional side view of another conventional gas-liquid mixing device. FIG. 11 is a vertical sectional side view of another example of the conventional gas-liquid mixing device. FIG. 11 is a vertical sectional side view of another example of the other conventional gas-liquid mixing device.

The following is an example of how the present invention can be implemented.

Note that parts that are the same as those in the background art are given the same reference numerals and their explanations are omitted.

The first embodiment of the present invention will be described with reference to Figures 1 to 3.

The gas-liquid mixing device of the present invention comprises a cylindrical mixing tank 1 with a bottom in which liquid is contained, a rotating shaft 2 suspended in the mixing tank 1, a mixing blade 10 provided at the lower end of the rotating shaft 2 for discharging liquid radially outward, a stationary blade 11 provided at the center of the bottom 1a of the mixing tank 1 for generating an upward flow, a liquid circulation pipe 12 connected to the outer peripheral wall of the mixing tank 1, for example, in the vertical direction, with both ends communicating with the inside and outside of the tank, a cooling means (not shown) for cooling the liquid circulation pipe 12, for example, a liquid transfer means such as a pump 13 provided in the liquid circulation pipe 12 for transferring the liquid in the liquid circulation pipe 12, and a fine bubble release means 14 made of a ceramic porous body or a fine bubble generating membrane provided in the circulation pipe 12, for example, downstream of the pump 13. 4 is a baffle, but may be omitted.

The outlet portion 12a of the liquid circulation pipe 12, which is connected to the mixing tank 1, is connected to the peripheral side wall of the mixing tank 1 where the circulation flow formed by the mixing blades 10 and the stationary blades 11 occurs.

The outlet portion 12a is connected, for example, to the lower portion of the peripheral side wall of the mixing tank 1.

The inlet 8b of the circulation pipe 8 is connected to the upper part of the peripheral side wall of the mixing tank 1.

The stirring blades 10 are, for example, four rectangular flat paddle blades 10a fixed radially to the lower end of the rotating shaft 2, and are provided at the top of the stirring tank 1 in the liquid.

The stator blades 11 are, for example, as shown in FIG. 2, made of linear strips 11a, and the strips 11a are fixed in parallel radial directions at a distance d from a radial line R passing through the center of the bottom 1a in the mixing tank 1, for example, four strips, and a gap is formed in the center of the bottom, which corresponds to the intersection of the strips 11a.

Since the present invention is configured as described above, when the agitator blade 10 is rotated, as shown in FIG. 3, the liquid from the agitator blade 10 is discharged radially outward, hits the inner circumferential surface 1b of the agitator tank 1, and generates a downward swirling flow along the inner circumferential surface of the agitator tank 1. The liquid then reaches the bottom 1a, moves to the center of the bottom 1a, and generates an upward flow in the center due to the stationary blades 11 of the bottom 1a. The upward liquid is then discharged radially outward by the agitator blade 7, and the liquid circulates within the agitator tank 1.

When the pump 9 is driven, the liquid in the mixing tank 1 is introduced into the circulation pipe 8 from the inlet 8b of the circulation pipe 8, and is then cooled by the cooling means. Then, the microbubbles are released into the liquid by the microbubble releasing means 14, and the liquid containing the microbubbles is released into the mixing tank 1 from the outlet 8a of the circulation pipe 8 by the driving force of the pump 8.

The outlet 8a is connected to the peripheral side wall of the mixing vessel 1 where the circulating flow formed by the mixing blades 10 and the stationary blades 11 occurs, so that the fine bubbles released into the mixing vessel ride on the circulating flow, rise at the center of the bottom, and ride on the circulating flow to mix the gas and liquid.

According to the present invention, the circulation force of the circulation pipe 8 is utilized to release fine bubbles into the stirring tank 1, and within the stirring tank 1, the fine bubbles can be circulated by being carried along in the circulation flow formed within the stirring tank 1, so that the stirring power and aeration power can be reduced and gas-liquid mixing can be achieved.

This makes it possible to reduce the energy consumption required for mixing power, for example, to a maximum of about 2/10.

In addition, the use of fine bubbles improves the gas absorption efficiency kLa, reducing the aeration flow rate required for cultivation and significantly reducing the aeration power required.

This dramatically reduces total energy consumption, enabling efficient operation of large culture tanks of 300 kL or more.

The above effects are also fully achieved even with a volume of 300kL or less.

In the above embodiment, an external cooling pump circulation flow was used, but the circulation pipe may be a circulation pipe that circulates the liquid in the tank outside the tank for purposes other than cooling, such as heating, concentration, dilution, addition, crystallization, etc., and may introduce the liquid in the mixing tank outside the mixing tank and then return the introduced liquid back into the mixing tank.

The circulation pipe itself may be for ventilation purposes.

The circulation pipe 8 may be connected to the mixing tank 1 not only vertically but also vertically or in other directions, and there is no particular limitation on where it is connected.

If there are multiple circulation pipes 8, each may be provided with the microbubble release means 14.

Moreover, multiple microbubble emitting means 14 may be provided within the circulation pipe 8.

The transport means for transporting the liquid through the circulation pipe may be a means other than a pump.

Reference Signs List 1 Agitation tank 1a Bottom 1b Inner surface 2 Rotation shaft 3 Agitation blade 4 Baffle 5 Vent pipe 6 Fine bubble emitting means 7 Cooling coil 8 Circulation pipe 9 Pump 10 Agitation blade 10a Blade plate 11 Stator blade 11a Band plate 12 Liquid circulation pipe 12a Outlet portion 12b Inlet portion 13 Transfer pump 14 Fine bubble emitting means

Claims (6)

A tank for containing a liquid;
a circulation pipe provided in the tank for introducing the liquid in the tank to the outside of the tank and then returning the liquid to the tank for circulation;
A liquid transfer means for transferring the liquid in the circulation pipe;
A gas-liquid mixing device comprising a ventilation means provided in the circulation pipe. A stirring blade provided in the stirring tank for discharging liquid radially outward;
The stirring vessel further includes a stator blade that generates an upward flow and is provided at the bottom of the stirring vessel,
2. The gas-liquid mixing device according to claim 1, wherein an outlet of the circulation pipe is connected to a wall of the vessel where a circulation flow formed by the mixing blades and the stationary blades occurs. The stirring blade is composed of a plurality of flat paddle blades arranged radially in the radial direction,
3. The gas-liquid mixing device according to claim 2, wherein the stator blade is made of a plurality of band-shaped plates arranged radially, and a gap is formed in a central portion corresponding to an intersection of the band-shaped plates. The gas-liquid mixing device according to claim 1, characterized in that the outlet of the circulation pipe is connected to the lower part of the peripheral side wall of the tank, and the inlet is connected to the upper part. The gas-liquid mixing device according to claim 1, characterized in that the ventilation means is formed from a membrane that generates fine bubbles. The gas-liquid mixing device according to claim 1, characterized in that a baffle extending in the vertical direction is provided on the inner peripheral surface of the mixing vessel.

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