Stirring device

Abstract

To provide a stirring device capable of performing good stirring even in a deep container. The device is provided with a cylindrical guide pipe that has a lower end located a predetermined distance above a nozzle arranged in a bottom wall, an upper end located at a predetermined depth from the liquid surface, and is open at both the lower and upper ends and extends in a substantially vertical direction. The inner diameter of the guide pipe is at least [1.5×(Q g / u B )×{1+(0.0608u L / Q g )×z 2}] 1 / 2 (Here, Q g is the gas flow rate, u B is the rising speed of the bubble, u L is the upward velocity of the liquid, and z is the vertical distance from the tip of the nozzle to the bottom of the guide pipe.

Description

[Technical field]

[0001] The present invention generally relates to an agitator, and more particularly, to an agitator capable of efficiently agitating a liquid even in a container having a deep bottom without requiring a mechanical drive source such as a propeller. [Background technology]

[0002] The present inventor has proposed various stirring devices capable of efficiently stirring liquids without requiring a mechanical drive source (see Patent Documents 1 to 4). The present inventor has also proposed a device that improves and develops the devices disclosed in Patent Documents 1 to 4, enabling good stirring even in deep containers (see Patent Document 5). [Prior art documents] [Patent documents]

[0003] [Patent Document 1] Patent No. 3058876 [Patent Document 2] Patent No. 4195782 [Patent Document 3] Patent No. 4384477 [Patent Document 4] Patent No. 4710070 [Patent Document 5] JP 2013-63375 A Summary of the Invention [Problem to be solved by the invention]

[0004] The stirring device of Patent Document 5, which is intended for deep containers, provides useful advantages, but has the following two problems to be solved. First, a problem occurs when a guide pipe installed in the device becomes clogged. That is, since there is an upper limit to the gas flow rate of the gas-liquid two-phase flow that can pass through the guide pipe, if the gas flow rate exceeds the upper limit, the excess gas overflows from the inlet of the guide pipe, preventing the occurrence of the swirling phenomenon, and efficient stirring cannot be expected. Second, a problem occurs when a guide pipe has a poor suction. That is, if the radial diffusion of the bubble jet generated by the gas ejected from the nozzle installed at the bottom of the container of the device becomes too large compared to the inlet of the guide pipe, the gas flow rate introduced into the guide pipe decreases, preventing the occurrence of the swirling phenomenon, and efficient stirring cannot be expected.

[0005] The present invention was developed in consideration of the above circumstances, and aims to provide a mixing device that enables good mixing even in deep containers by solving the two problems mentioned above. [Means for solving the problem]

[0006] The operation principle of the stirring device of the present invention will be described with reference to FIG. 8. When a cylindrical container equipped with a single-hole nozzle at the bottom is filled with liquid and gas is blown into the liquid from the nozzle, an ascending bubble jet is formed. The inventor of the present invention discovered that, under certain conditions, this ascending bubble jet generates a swirling phenomenon that is favorable for stirring the liquid, as shown in Patent Document 1. That is, if the inner diameter of the cylindrical container is D and the difference in height between the tip of the nozzle and the liquid surface is 0H1, when the relationship between D and 0H1 is about 0.3<0H1 / D<about 1, the radial displacement of the bubble jet is relatively small, a swirling phenomenon with a short period occurs, and the liquid in the cylindrical container behaves similarly to sloshing. Here, sloshing refers to a phenomenon in which vibrations of the liquid are induced by vibrating the container in the axial or radial direction. It is presumed that the above-mentioned swirling phenomenon is induced by the periodic vibration of the gas to the liquid accompanying the generation and rise of bubbles.

[0007] When the ratio OH1 / D is less than about 0.3, the radial displacement of the bubble jet is extremely small, and the swirl is insufficient to agitate the liquid. When the ratio OH1 / D is greater than about 1, the swirl is unstable and sufficient agitation effect cannot be obtained.

[0008] Since the above-mentioned swirling phenomenon is induced by the periodic vibration of the liquid by the bubbles, in order for the swirling phenomenon favorable for agitating the liquid to occur, the flow rate of the injected gas must be equal to or higher than a critical value and be lower than the level at which the bubbles blow through the liquid surface. Note that the term "blow through" used in this specification means the phenomenon in which the gas injected into the liquid from the nozzle creates an air column and escapes from the liquid surface to the outside.

[0009] The inventors have calculated the critical value of the gas flow rate as follows. Research on sloshing has shown that vibration of a container induces waves on the liquid surface, and these waves are transmitted to the inside of the liquid via viscosity, causing movement inside the liquid. It is therefore presumed that the swirling stops when the wave phenomenon on the liquid surface is suppressed. According to the inventors' experiments, it can be concluded that the main part of the vibration force is the force that bubbles exert on the liquid almost periodically as they rise and leave the liquid surface. It is assumed that this force depends on the inertial force of the rising liquid. Furthermore, surface tension is likely to be involved in the force that tries to stop the wave motion. The inventors have calculated the Weber number W, defined as the ratio of the inertial force of the liquid to the surface tension, e =ρ L Q g 2 / (σ L D 3 ) is 10 -5 It has been confirmed through experiments that if the Weber number W in the above formula is greater than or equal to this, the swirling phenomenon that is favorable for stirring the liquid will occur. e =10 -5 is the critical value, where ρ L is the density of the liquid, Q g is the gas injection flow rate, σ L is the surface tension of the liquid and D is the inner diameter of the cylindrical container.

[0010] On the other hand, when the liquid above the nozzle swirls in one direction as shown by arrow A in Figure 8(b), due to the law of conservation of angular momentum, the liquid below the nozzle swirls in the opposite direction as shown by arrow B in Figure 8(b). The swirling flow B below the nozzle stabilizes the swirling flow A above the nozzle, and even if the speed of swirling flow A decreases or becomes turbulent due to the introduction of solid matter or the like into swirling flow A, the original state can be easily restored as long as swirling flow B exists. For this reason, it is preferable to provide an area of ​​a certain depth below the nozzle.

[0011] As described above, it was found that by filling a cylindrical vessel equipped with a single-hole nozzle at the bottom with liquid and injecting gas into the liquid from the nozzle, a swirling phenomenon that is favorable for stirring the liquid occurs under certain conditions, but when the cylindrical vessel is deep (i.e., the depth from the tip of the nozzle to the bottom wall of the cylindrical vessel is deep), it is difficult to say that the stirring of the liquid at the bottom of the cylindrical vessel is necessarily sufficient. Therefore, the present inventor proposed an apparatus that stirs the liquid in the vessel well even when the cylindrical vessel is deep by providing a guide pipe that extends vertically in the cylindrical vessel, with its lower end located a certain distance above the tip of the nozzle and its upper end located at a specified depth from the liquid surface (Patent Document 5).

[0012] As described above, the device of Patent Document 5 had two problems to be solved: "clogging" of the guide pipe and "poor suction" of the guide pipe. The present inventor solved these problems as follows.

[0013] (Guide pipe "clogging") When a mixture of gas (bubbles) and liquid (gas-liquid two-phase flow) rises in a vertical pipe, the rising speed of the bubbles is B The Akagawa-Sakaguchi equation below is known as an empirical formula that expresses the void fraction of a two-phase flow (Hiroshi Akagawa and Tadashi Sakaguchi: Study on the void fraction characteristics of gas-liquid two-phase flow (3rd report), Transactions of the Japan Society of Mechanical Engineers, 31-223 (1965), pp. 601-607). About large bubbles B= 1.25 × (j g +j L ) (1) About small air bubbles B = 1.10 × (j g +j L ) (2) where j g is the superficial velocity of the gas in the guide pipe, j L is the superficial velocity of the liquid in the guide pipe, and is expressed by the following equations. j g = (4Q g ) / (πd g 2 ) (3) j L = (4Q L ) / (πd g 2 ) (4) Here, Q g is the gas injection flow rate, Q L is the flow rate of liquid induced by bubbles in the bubble jet, d g is the inner diameter of the guide pipe.

[0014] In the present invention, the rising speed of the bubble u B To express this, we use the following approximate formula, which is the average of formula (1) and formula (2). u B = 1.18 × (j g +j L ) (5)

[0015] Substituting equations (3) and (4) into equation (5) and rearranging it, the inner diameter of the guide pipe, d g is expressed by the following equation. d g = [ 1.5×(Q g / u B )×{ 1+(Q L / Q g )}] 1 / 2 (6)

[0016] On the other hand, the rising speed of the bubble, u B and the liquid flow rate Q L It is known that the flow rate of the round vertical bubble plume is given by the following equation (Manabu Iguchi, Hiroaki Takeuchi, Zenichiro Morita: Flow Field in a Bottom-Blown Water-Air Bubble Jet in a Cylindrical Vessel, Tetsu-to-Haganen, 76-5 (1990), pp.699-706 / Marco ASC Castello-Branco and K. Schwerdtfeger: Large-Scale Measurements of the Physical Characteristics of Round Vertical Bubble Plumes in Liquids, Metallurgical and Materials Transactions B, 25B (1994), pp. 359-371). u B =(Q g g 2 ) 1 / 5 ×{1.60×(z / z 0CS ) -2.04 +1.82×(z / z 0CS ) -0.08} However, (z / z 0CS )> 0.6 (7) z 0CS = 6.8 × d ni ×{(Q g 2 ρ g ) / (gd ni 5 ρ L )} 0.272 (8) Q L =3.6×u L ×b u 2 (9) u L =(Q g g 2 ) 1 / 5 ×{ 0.95 × (z / z 0CS ) -2.30 +1.10×(z / z 0CS ) -0.08} However, (z / z 0CS )> 0.8 (10) b u =0.13×z (11) Here, Q g is the gas injection flow rate, u B As mentioned above, u is the rising speed of bubbles when a mixture of gas (bubbles) and liquid rises in a vertical pipe. L is the upward velocity of the liquid on the central axis of the vertical pipe when the mixture of gas (bubbles) and liquid rises inside the vertical pipe, z is the distance from the tip of the nozzle to the bottom of the guide pipe (H1 in Figure 1), g is the acceleration of gravity, d ni is the inner diameter of the nozzle, ρ g is the density of the gas, ρ L is the density of the liquid.

[0017] Substituting equations (9) and (11) into equation (6), we obtain the following equation. d g = [1.5 × (Q g / u B ) ×{1+(0.0608u L / Q g )×z 2}] 1 / 2 (12) That is, the inner diameter of the guide pipe d g By making the diameter at least that given by equation (12), it is possible to prevent the guide pipe from becoming “clogging”.

[0018] (Guide pipe "poor suction") When gas is injected from a nozzle into a liquid in a cylindrical container, many bubbles are generated near the tip of the nozzle and rise while dispersing in the radial direction. In order to quantitatively determine the dispersion of these bubbles in the radial direction, we focus on gas hold-up α. Looking at point P in the bubble jet, bubbles and liquid pass by alternately, and gas hold-up α is the percentage of the time that bubbles pass through the entire measurement time, and is expressed as a percentage. For example, if point P is always inside the bubbles, gas hold-up α is 100%, and if point P is always inside the liquid, gas hold-up α is 0%.

[0019] It is known that the gas holdup α can be obtained by the following formula: α=α cl ×exp{-0.6931×(r 2 / b α 2 )} (13) Here, α cl is the value of the gas holdup α on the central axis, r is the radial coordinate, b α is the half-width at half maximum of the gas holdup α, and α cl and b α Under the blowing conditions targeted in the present invention, these are given by the following equations. α cl =50×(z / z0) -1.0 (14) b α =b α (z0) × (z / z0) 0.5 =0.42×(Q g 2 / g ) 1 / 5 ×(z / z0) 0.5 (15) Here, z0 is the value of z at which the gas holdup α becomes 50% and is given by the following equation. z0=5×d ni ×{(Q g 2 ρ g ) / (gdni 5 ρ L )} 0.30 (16)

[0020] On the other hand, the width of the radial dispersion of the bubbles W g It is known that can be approximated by the following equation (Iguchi Manabu, Kawabata Hirotoshi, Iwasaki Toshikatsu, Nozawa Kentaro, Morita Zenichiro: Bubble characteristics in the momentum-dominated region of a bottom-blown water-air bubbly jet in a cylindrical vessel, Tetsu-to-Haganen, 76-6(1990), pp. 840-847). W g =4b α (17)

[0021] In order for all the gas coming out of the nozzle to be sucked into the guide pipe, the diameter of the lower end of the guide pipe D g is the radial width of the bubble dispersion W g It is necessary that the D g > W g (18) Therefore, for all the gas coming out of the nozzle to be sucked into the guide pipe, D g > 4b α (19) must be met. In other words, by making the inside diameter of the lower end of the guide pipe at least the diameter given by equation (19), it is possible to prevent "poor suction" of the guide pipe.

[0022] The stirring device according to claim 1 of the present application is provided with a cylindrical container having an inner diameter D or a polygonal container having a polygonal planar shape with an inscribed circle diameter D. A liquid is contained in the cylindrical container or the polygonal container, a nozzle for blowing gas into the liquid is disposed at approximately the center of the bottom wall of the cylindrical container or the polygonal container, and a flow rate Q of the gas blown into the liquid from the nozzle is gBut, ρ L Q g 2 / (σ L D 3 )=10 -5 (where ρ L is the density of the liquid, σ L is a flow rate that satisfies the surface tension of the liquid) and is a flow rate that is not greater than a flow rate at which bubbles of the gas do not blow through the surface of the liquid, the nozzle has a lower end located a predetermined distance above the tip of the nozzle and an upper end located at a depth H3 from the liquid surface, the lower end and the upper end are open and the nozzle has a cylindrical guide pipe that extends in a substantially vertical direction, and the inner diameter of the guide pipe is at least [1.5×(Q g / u B )×{1+(0.0608u L / Q g )×z 2}] 1 / 2 (where u B is the rising speed of the bubbles when the mixture of bubbles and liquid rises in the guide pipe, u L is the upward velocity of the liquid on the central axis of the guide pipe when a mixture of air bubbles and liquid rises inside the guide pipe, and z is the vertical distance from the tip of the nozzle to the lower end of the guide pipe), and the ratio H3 / D of H3 to the inner diameter or inscribed circle diameter D is in the range of 0.3 to 1.

[0023] The mixing device according to claim 2 of the present invention is the mixing device according to claim 1, further comprising an expanded diameter portion at the lower end of the guide pipe, the inner diameter of the expanded diameter portion being at least 4b α (where b α is selected to be a diameter given by the half width at half maximum of the gas holdup, which represents the degree of dispersion of the bubbles in the radial direction.

[0024] The stirring device described in claim 3 of the present application is characterized in that, in the stirring device of claim 1 or claim 2, the bottom wall of the cylindrical container or the polygonal container has a flat bottom or a round bottom.

[0025] The agitation device according to claim 4 of the present invention is the agitation device according to any one of claims 1 to 3, characterized in that the gas is air or a reactive gas. Effect of the Invention

[0026] According to the agitator of the present invention, a good agitation effect can be obtained even if the container is deep. The agitator of the present invention does not require a driving source such as a propeller, and therefore has an extremely simple structure. Therefore, the agitator of the present invention can keep manufacturing and maintenance costs low, and can reduce the time and effort required for maintenance and inspection. [Brief description of the drawings]

[0027] [Figure 1] 1 is a schematic diagram showing an entirety of a stirring device according to a preferred embodiment of the present invention. [Diagram 2] 1 is a series of diagrams showing an example of a mounting form of a guide pipe. [Diagram 3] 13A and 13B are diagrams showing modified forms of the lower end of the guide pipe. [Figure 4] FIG. 2 is a diagram showing an operating state of the stirring device of FIG. [Diagram 5] 5 is an enlarged view showing the periphery of the lower end of the guide pipe in FIG. 4. [Figure 6] FIG. 13 is a diagram showing a modified example of the nozzle arrangement. [Figure 7] FIG. 2 is a schematic diagram showing the entire stirring device when the container has a round bottom. [Figure 8] FIG. 2 is a diagram for explaining the operating principle of the stirring device in FIG. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0028] Next, a stirring device according to a preferred embodiment of the present invention will be described with reference to the drawings. The stirring device according to the preferred embodiment of the present invention, generally designated by reference numeral 10 in Fig. 1, includes a cylindrical container 12 having a side wall 12a and a bottom wall 12b. The cylindrical container 12 has an inner diameter D as shown in Fig. 1. The liquid to be stirred is contained in the cylindrical container 12 such that the height from the bottom wall 12b to the liquid level is H1+H2+H3.

[0029] A nozzle 14 is disposed approximately at the center of the bottom wall 12b of the cylindrical container 12, and the nozzle 14 is connected to an air compressor (not shown). This allows air supplied from the air compressor to be sprayed from the nozzle 14 into the liquid.

[0030] The agitator 10 also includes a guide pipe 16 that extends substantially vertically with a length H2, with its lower end 16a located at a distance z above the tip of the nozzle 14 and its upper end 16b located at a depth H3 below the liquid surface. The guide pipe 16 is generally cylindrical and has an inner diameter d g In the embodiment of the stirrer 10 shown in Fig. 1, the tip of the nozzle 14 and the bottom wall 12b of the cylindrical container 12 are located at the same height, so the distance z from the tip of the nozzle 14 to the lower end 16a of the guide pipe 16 is equal to the distance H1 from the bottom wall 12b to the lower end 16a of the guide pipe 16.

[0031] Inner diameter d of guide pipe 16 g is selected to be at least the diameter given by equation (12). This makes it possible to avoid "clogging" of the guide pipe 16.

[0032] 2(a) to 2(d) are a series of diagrams showing a state in which the guide pipe 16 is supported by the support member 18 at a position spaced a distance z above the tip of the nozzle 14 on the bottom wall 12b of the cylindrical container 12. In the embodiment shown in FIG. 2(a) and FIG. 2(b), the support member 18 is composed of four columns arranged at 90° intervals in the circumferential direction. In the embodiment shown in FIG. 2(c) and FIG. 2(d), the support member 18 is composed of three columns arranged at 120° intervals in the circumferential direction. Note that the embodiments shown in FIG. 2(a) to FIG. 2(d) are illustrative examples of the details of the configuration of the support member 18, and are not limited to the configurations shown in the figures as long as they can support the guide pipe 16 at a predetermined position.

[0033] Preferably, the lower end 16a of the guide pipe 16 is provided with an expanded diameter portion 16c having a larger diameter than the other portions, as shown in FIG. g is selected to be at least the diameter given by equation (19). This makes it possible to avoid "poor suction" of the guide pipe 16.

[0034] In the embodiment shown in FIG. 3(a), the expanded diameter portion 16c has an inner diameter D g After a certain length of the part, the inner diameter d g However, if the inner diameter of the lowest part can secure the required diameter, for example, as shown in Figure 3(b), the inner diameter D g From the part of the inner diameter d g It may also be shaped so as to taper gradually to

[0035] The ratio H3 / D of the depth H3 from the liquid level to the upper end 16b of the guide pipe 16 to the inner diameter D of the cylindrical container 12 is in the range of about 0.3 to about 1. Preferably, the ratio H3 / D is about 0.5.

[0036] 4 is a schematic diagram showing a state in which air is injected from the nozzle 14 in the agitator 10 through the guide pipe 16 into the liquid, causing the liquid to swirl as shown by the arrow A. In this case, the flow rate Q of the air injected from the nozzle 14 is g is ρ L Q g 2 / (σ L D 3 )=10 -5 The flow rate is equal to or greater than the flow rate that satisfies the above requirement, and is equal to or less than the flow rate at which air bubbles blow through the liquid surface.

[0037] As described above, the liquid below the upper end 16b of the guide pipe 16 swirls in the opposite direction as indicated by the arrow B in FIG. 4 due to the law of conservation of angular momentum.

[0038] (Example) The inner diameter D of the cylindrical container 12 is 30.8 cm, and the inner diameter d of the nozzle 14 is ni = 0.8 cm, the distance z from the tip of the nozzle 14 to the lower end 16a of the guide pipe 16 = 2.5 cm, the gas injection flow rate Q g =250cm 3 / s (=15L / min) as an example, the inner diameter d of the nozzle 14 where no clogging occurs is g And the inner diameter D of the expanded diameter portion 16c where "poor suction" does not occur g We will estimate the following.

[0039] From equation (8), z 0CS =6.8×0.8×{(250 2 x1.23x10 -6 ) / (980×0.8 5 x998x10 -6 )} 0.272 =3.69cm From equation (7), u B =(250×980 2 ) 1 / 5 ×{1.60×(2.5 / 3.69 ) -2.04+1.82×(2.5 / 3.69 ) -0.08} =47.4×(3.54+1.88) =257cm / s From equation (10), u L =(250×980 2 ) 1 / 5 ×{0.95×(2.5 / 3.69 ) -2.30 +1.10×(2.5 / 3.69 ) -0.08} =47.4×(2.32+1.13) =164cm / s From equation (12), d g =[1.5×(250 / 257 )×{1+(0.0608×164 / 250)×2.5 2}] 1 / 2 =1.35cm Therefore, the inner diameter d of the guide pipe 16 g By making the length at least 1.35 cm, it is possible to prevent the guide pipe 16 from becoming "clogging."

[0040] From equation (16), z0 = 5 × 0.8 × {(250 2 x1.23x10 -6 ) / (980×0.8 5 x998x10 -6 )} 0.30 =2.61cm From equation (15), b α =0.42×(250 2 / 980) 1 / 5 ×(2.5 / 2.61) 0.5 =0.943cm From equation (17), W g =4×0.943 =3.77cm Therefore, the inner diameter D of the expanded diameter portion 16c g By making the length at least 3.77 cm, it is possible to prevent "poor suction" from occurring in the guide pipe 16.

[0041] Next, the operation of the agitator 10 configured as above will be described with reference mainly to Figures 4 and 5. In the agitator 10, when air is blown into the liquid from the nozzle 14, the air passes through the guide pipe 16 and is ejected from the upper end 16b of the guide pipe 16 into the liquid. g is selected, the air at the lower end 16a of the guide pipe 16 is sucked into the guide pipe 16 together with the liquid, and is sprayed from the upper end 16b into the liquid due to: [1] the "ejector effect" which occurs when the fluid around the jet is entrained in the jet when the fluid is introduced from the nozzle in a jet state into the same fluid or another fluid; and [2] the "chimney effect" which occurs when the apparent density of the gas-liquid two-phase flow inside the guide pipe 16 is smaller than the density of the liquid outside the guide pipe 16.

[0042] In this manner, the liquid located near and above the upper end 16b of the guide pipe 16 swirls as indicated by arrow A, and the liquid located below swirls in the opposite direction as indicated by arrow B.

[0043] On the other hand, the liquid located around the lower end 16a of the guide pipe 16 is drawn into the lower end 16a of the guide pipe 16 along with the air blown into the liquid from the nozzle 14, so that the liquid is given a motion as shown by the arrows. As a result, the liquid located at the bottom of the cylindrical container 12 is also stirred.

[0044] By providing an enlarged diameter section 16c at the lower end 16a of the guide pipe 16 (see Figures 3(a) and (b)), "poor suction" of the guide pipe 16 is avoided and substantially all of the air blown in from the nozzle 14 is sucked into the guide pipe 16, thereby making it possible to stir the liquid in the cylindrical container 12 more efficiently.

[0045] The present invention is not limited to the above-described embodiments of the invention, and various modifications are possible within the scope of the invention described in the claims, and it goes without saying that these modifications are also included within the scope of the present invention.

[0046] For example, in the above embodiment, the planar shape of the container 12 is a circle, but a polygonal container having an n-sided (n≧3) planar shape may be used instead of the cylindrical container 12. In this case, D is the diameter of the inscribed circle of the n-sided shape.

[0047] In addition, in the form of the stirring device 10 shown in Figure 1, the tip of the nozzle 14 and the bottom wall 12b of the cylindrical container 12 are located at the same height, but if there is a possibility that solid matter will accumulate at the bottom of the cylindrical container 12, it is preferable to configure the nozzle 14 so that the tip of the nozzle 14 is located slightly above the bottom wall 12b of the cylindrical container 12 so that solid matter does not enter the nozzle 14 and cause it to become clogged (see Figure 6).

[0048] In the above embodiment, the bottom wall 12b of the cylindrical container 12 is flat, but as shown in FIG. 7, the bottom wall 12b of the cylindrical container 12 may be rounded.

[0049] Furthermore, in the above embodiment, the gas sprayed from the nozzle is air, but in cases where it is intended to react while stirring the liquid, the gas sprayed from the nozzle may be a reactive gas such as oxygen gas depending on the purpose. [Explanation of symbols]

[0050] 10 Stirring device 12 Cylindrical container 12a side wall 12b Bottom wall 14 Nozzles 16 Guide pipe 16a Bottom end 16b Top edge 16c Expanded diameter part 18 Support member

Claims

1. A stirring device having a cylindrical container with an inner diameter D or a polygonal container having a polygonal planar shape with an inscribed circle diameter D, wherein a liquid is contained in the cylindrical container or the polygonal container, a nozzle for blowing a gas into the liquid is disposed at approximately the center of a bottom wall of the cylindrical container or the polygonal container, and a flow rate Q of the gas blown into the liquid from the nozzle is ｇ But, ρ Ｌ Q g 2 / (σ Ｌ D 3 )=10 -5 (where ρ Ｌ is the density of the liquid, σ Ｌ is the surface tension of the liquid) and is equal to or greater than a flow rate at which bubbles of the gas do not blow through the surface of the liquid, The lower end is located at a predetermined distance above the tip of the nozzle, and the lower end is located at a depth H from the liquid surface. ３ a cylindrical guide pipe having an upper end located at the position of the lower end, the lower end and the upper end being open, and extending in a substantially vertical direction; The inner diameter of the guide pipe is at least [1.5 × (Q g / u B ) × {1 + (0.0608u L / Q g ) x z 2 }] 1 / 2 (where u B is the rising speed of the bubbles when the mixture of bubbles and liquid rises in the guide pipe, u L is the upward velocity of the liquid on the central axis of the guide pipe when the mixture of air bubbles and liquid rises inside the guide pipe, and z is the vertical distance from the tip of the nozzle to the lower end of the guide pipe), The H ３ and the ratio H of the inner diameter or the inscribed circle diameter D ３ / D is in the range of 0.3 to 1.

2. The guide pipe has an expanded diameter portion at the lower end thereof, and the inside diameter of the expanded diameter portion is at least 4b α (where b α 2. The stirring device according to claim 1, wherein the diameter is selected to be a diameter given by a half-width at half maximum of a gas holdup which represents a degree of dispersion of the bubbles in the radial direction.

3. 3. The stirring device according to claim 1, wherein the bottom wall of the cylindrical container or the polygonal container has a flat bottom or a round bottom.

4. 4. The stirring device according to claim 1, wherein the gas is air or a reactive gas.

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