Stirring device and stirring method

Abstract

A stirring device 1 comprises a stirring blade 3 for stirring, by rotation, a fluid to be stirred that is accommodated in a stirring tank 2. The stirring blade 3 is provided with a plurality of blade parts 31A-31D that are disposed apart from each other in the height direction of the stirring tank 2. Each of the blade parts 31A-31D is provided with blades 33A-33D for generating a flow of the fluid to be stirred, the flow having a component in the height direction of the stirring tank 2 due to rotation. The height-direction dimensions of the blades 33A-33D are greater or lesser in the blade parts 31A-31D closer to a bottom part 22 of the stirring tank 2. The blades 33A-33D in the respective blade parts 31A-31D generate the flow of the fluid to be stirred, the flow having a component in the height direction toward the bottom part 22 of the stirring tank 2 due to rotation, and the height-direction dimensions of the blades 33A-33D are greater in the blade parts 31A-31D closer to the bottom part 22 of the stirring tank 2.

Description

Stirring device and stirring method

[0001] The present disclosure relates to a stirring device and the like.

[0002] Patent Document 1 discloses an agitation device that produces a latex (also referred to as an emulsion) in which polymer (high molecular weight) particles are dispersed in a medium such as water by a polymerization reaction of a monomer in an agitation tank.

[0003] Japanese Patent Application Publication No. 10-33966

[0004] In order to efficiently release the reaction heat in the polymerization reaction (hereinafter also referred to as polymerization heat) outside the stirring vessel, for example, a stirring vessel is often used in which the ratio of the liquid level height L of the stirred fluid to the diameter D of the stirring vessel is significantly greater than 1. In order to effectively stir the stirred fluid in such a vertically long stirring vessel, Patent Document 1 proposes the use of stirring blades with a special shape.

[0005] The present disclosure has been made in consideration of these circumstances, and aims to provide an agitation device, etc. that can effectively agitate the fluid to be stirred in a stirring tank without using a specially shaped agitator blade.

[0006] In order to solve the above problems, a stirring device according to one embodiment of the present invention includes a stirring blade that rotates to stir a fluid contained in a stirring tank. The stirring blade includes a plurality of blade portions that are spaced apart in the height direction of the stirring tank. Each blade portion includes a vane that generates a flow of the fluid to be stirred having a component in the height direction of the stirring tank by rotation. The height dimension of the vane is larger or smaller for blade portions closer to the bottom of the stirring tank.

[0007] As will be described in detail later, when the height dimensions of the blades of multi-stage blade sections arranged at intervals in the height direction of the stirred tank are equal, for example, flows from above and below collide between two blade sections adjacent in the height direction, forming a flow partition and deteriorating the stirring performance of the stirred tank as a whole.In contrast, according to this embodiment, the height dimensions of the blades closer to the bottom of the stirred tank are made larger or smaller, in other words, the height dimensions of the blades are monotonically increased or decreased along the height direction, thereby improving the stirring performance of the stirred tank as a whole.

[0008] Another aspect of the present invention is a stirring method. This method is a stirring method in a stirring device equipped with a stirring blade that stirs a stirred fluid contained in a stirring vessel by rotation, and the stirring blade has a plurality of blade portions arranged at intervals in the height direction of the stirring vessel, with blade portions having blades with larger or smaller height dimensions closer to the bottom of the stirring vessel. The rotation of each blade generates a flow of the stirred fluid having a height component in the height direction of the stirring vessel.

[0009] Any combination of the above components, or any conversion of these expressions into methods, devices, systems, recording media, computer programs, etc., are also encompassed within the present disclosure.

[0010] According to the present disclosure, the fluid to be stirred in the stirring tank can be effectively stirred without using stirring blades with special shapes.

[0011] 1 is a schematic diagram showing the configuration of a stirring device according to a first embodiment; FIG. 2 is a comparative example of the stirring device of FIG. 1; FIG. 3 is a flow pattern of the first embodiment; FIG. 4 is a flow pattern of a comparative example; FIG. 5 is a schematic diagram showing the configuration of a stirring device according to a modified example of the first embodiment.

[0012] Hereinafter, with reference to the drawings, a detailed description will be given of a mode for carrying out the present disclosure (hereinafter also referred to as an embodiment). In the description and / or drawings, the same or equivalent components, members, processes, etc. are designated by the same reference numerals, and redundant description will be omitted. The scale and shape of each part shown in the drawings are set for convenience to simplify the description, and should not be interpreted as limiting unless otherwise specified. The embodiment is an example and does not limit the scope of the present disclosure in any way. All features and combinations thereof described in the embodiment are not necessarily essential to the present disclosure.

[0013] FIG. 1 is a schematic diagram illustrating the configuration of an agitation device 1 according to a first embodiment of the present disclosure. In this embodiment, the agitation device 1 is installed vertically, which corresponds to the up-down, longitudinal, and height directions in FIG. 1 . The terms up-down, longitudinal, height, and vertical are used interchangeably, and the terms left-right, lateral, and horizontal are also used interchangeably. Note that the present disclosure is also applicable to an agitation device 1 that is not installed vertically. In such cases, the up-down, longitudinal, and height directions are different from the vertical direction, and the left-right, lateral, and horizontal directions are different from the horizontal direction. Furthermore, as described below, the rotation shaft 30 of the agitation impeller 3 is provided in the up-down, longitudinal, height, and vertical directions, and therefore the up-down, longitudinal, height, and vertical directions are also referred to as axial directions. Furthermore, the left-right, lateral, and horizontal directions are also referred to as radial directions, because the left-right, lateral, and horizontal directions determine the diameter of the agitation vessel 2 and the agitation impeller 3.

[0014] The stirring device 1 includes a stirring tank 2 containing a fluid to be stirred (fluid to be stirred) and a stirring impeller 3 that rotates to stir the fluid in the stirring tank 2. The stirring tank 2 includes a cylindrical straight body portion 21 located at the top and extending in the axial direction, and a bottom portion 22 located below and continuous with the straight body portion 21. The inner peripheral wall or side wall of the straight body portion 21 has a circular cross section when viewed from above (axially), and its diameter D is hereinafter also referred to as the vessel diameter D of the stirring tank 2. Note that the cross section of the straight body portion 21 and / or the stirring tank 2 when viewed from above may have any non-circular shape. In this case, the vessel diameter D of the stirring tank 2 may be the diameter of the inscribed circle of the cross-sectional shape, the diameter of the circumscribed circle of the cross-sectional shape, or an average or intermediate value thereof. At least a portion of the upper portion of the straight body portion 21 is open (not shown) so that the fluid to be stirred can be introduced, and the opening can be closed with a lid or the like while the fluid is being stirred by the stirring impeller 3. The fluid to be stirred may be supplied into the stirring tank 2 from a fluid supply port such as a supply nozzle that may be provided on the side of the body portion 21, for example.

[0015] The bottom 22 of the stirring tank 2 may be formed in an inverted cone shape or an inverted truncated cone shape whose diameter decreases downward. Alternatively, the bottom 22 may be formed in a flat shape with the axial direction as the normal. In the illustrated example, the bottom 22 is formed in a curved shape that bulges downward from the lower end of the cylindrical body 21. The bulging end of the curved shape forms the bottom of the stirring tank 2 at the center of the bottom 22. An outlet (not shown) may be provided at the bottom of the stirring tank 2 through which the fluid in the stirring tank 2 can be discharged outside the stirring device 1. This outlet is configured to be openable and closable by an outlet opening / closing device such as a valve. When the fluid to be stirred is introduced into the stirring tank 2 and retained therein, or when the fluid before discharge is stirred with the stirring blades 3 to promote mixing or chemical reaction or to homogenize the concentration, a valve or the like controlled to a closed state closes the outlet. Furthermore, when the fluid to be discharged after the mixing or chemical reaction is substantially completed and the concentration is homogenized is discharged while being stirred with the stirring blades 3 as needed, a valve or the like controlled to an open state opens the outlet. The stirred fluid may be discharged from an opening in the upper part of the stirred tank 2 when the lid is open. The stirred fluid may also be discharged to the outside of the stirred tank 2 from a fluid outlet such as a discharge nozzle that may be provided on the side of the barrel portion 21.

[0016] The horizontal boundary between the approximately cylindrical barrel portion 21 and the curved bottom portion 22 is also referred to as the tangent line TL. Hereinafter, the vertical distance L between the lowest part of the stirred tank 2 (bottom 22) and the surface or liquid level LL of the fluid in the stirred tank 2 is also referred to as the liquid level height or reference height. In this embodiment, the ratio L / D of the vertical liquid level L of the stirred fluid in the stirred tank 2 to the radial vessel diameter D of the stirred tank 2 is 1.2 or greater. Such a vertically elongated stirred tank 2 allows for a large sidewall area that serves as a heat dissipation surface, making it suitable for stirring the stirred fluid (chemical reaction) that involves a large amount of reaction heat. An example of such a chemical reaction is polymerization. When the bottom 22 is flat, the vertical distance L between the flat bottom 22 (bottom plate) and the surface or liquid level LL of the fluid in the stirred tank 2 may also be referred to as the liquid level height.

[0017] The stirred fluid for polymerization contains water and a monomer to be polymerized. In this embodiment, the monomer is exemplified by polyol (polyhydric alcohol), which is a raw material for polyurethane and the like as a polymer, but is not limited to this. The polyol dispersed in water in the stirring tank 2 is typically mixed with isocyanate in a subsequent stage (not shown) of the stirring device 1 to produce polyurethane. In a typical polymerization reaction, an emulsifier (such as a surfactant) and a polymerization initiator (such as a radical generator) are also added to the stirred fluid. The physical properties of such a stirred fluid are arbitrary, but the stirred fluid in this embodiment is, for example, a polyol having a density of 1000 kg / m 3 The viscosity is 1000 cP. The water in the fluid being stirred is dispersed uniformly in the polyol by the stirring of the rotating stirring blades 3, and a homogeneous polymer is obtained through the reaction with the isocyanate.

[0018] The agitator blade 3 is rotatably mounted around a vertical rotation shaft 30 that substantially coincides with the vertical central axis of the agitator tank 2. Although not shown, a rotation drive unit such as a motor that generates rotational power and a rotational power conversion unit such as a transmission or reducer that converts the rotational power into a desired number of rotations (or rotational speed) or torque are provided above the rotation shaft 30. A lower bearing may be provided below the rotation shaft 30.

[0019] A baffle 4 is provided near the inner peripheral wall of the straight body portion 21 in the stirring vessel 2, extending in a substantially axial direction over most of the liquid level L and projecting in a substantially radial direction toward the central axis of the stirring vessel 2 (or the rotation axis 30 of the stirring blade 3). As shown in the example shown, multiple baffles 4 may be provided along the circumferential direction. The stirred fluid rotated in the circumferential direction by the stirring blade 3 hits the baffle 4, also called a baffle plate, preventing the stirred fluid from rotating together with the stirring blade 3 due to inertia. Note that the baffle 4 must not interfere with the rotation of the stirring blade 3 itself, and is arranged in a radial range outside the rotation areas of the multiple blade portions 31A to 31D described below.

[0020] The agitator blade 3 has a plurality of (four in the example of FIG. 1 ) blade portions 31A to 31D (hereinafter collectively referred to as blade portions 31) that are spaced apart in the height direction (axial direction). In this embodiment, an example will be described in which the blade diameter d of each of the blade portions 31A to 31D is substantially equal, but the blade diameters d of each of the blade portions 31A to 31D may be different from one another. Each of the blade portions 31A to 31D is a small agitator blade that has a substantially linear or substantially planar blade portion main body 32A to 32D (hereinafter collectively referred to as blade portion main body 32) that extends generally radially from the rotating shaft 30.

[0021] Each of the blade bodies 32A to 32D (or the connecting portion between each of the blade bodies 32A to 32D and the rotating shaft 30) is provided with one or more (two in the example of FIG. 1 ) blades 33A to 33D (hereinafter collectively referred to as blades 33) that generate a flow of the stirred fluid having a predetermined directional component by rotation around the rotating shaft 30. The blades 33 are formed, for example, by a substantially rectangular plate, and the normal direction of the stirring surface is inclined with respect to both the axial and radial directions, so that a flow of the stirred fluid having an axial component (axial flow) is generated by rotation around the rotating shaft 30. In the example of FIG. 1 , the blades 33 of each blade 31 rotate integrally with the rotating shaft 30 and the blade body 32 in the illustrated rotation direction R (clockwise direction in top view), thereby generating a downward axial flow FA of the stirred fluid having a height direction component (downward component) toward the bottom 22 of the stirring tank 2. Ｄ ~FD Ｄ (Hereinafter, this will be collectively referred to as the downward axial flow F Ｄ 1 illustrates the blade portion 31 as an inclined paddle blade in which the normal direction of the stirring surface of one or more blades 33 is inclined at an acute angle to both the axial direction and the radial direction, but some or all of the blade portions 31A to 31D may be configured as axial flow blades such as hydrofoils.

[0022] Lower axial flow F Ｄ The blade 33 that generates the downward axial flow F is provided on the radial center side of the agitating blade 3, i.e., on the rotating shaft 30 side. ＤOn the other hand, as will be described later, on the radial outer periphery of the agitating blade 3, i.e., in the vicinity of the inner circumferential wall of the agitating vessel 2 or the baffle 4, the agitated fluid circulating or convecting in the agitating vessel 2 flows downward in the axial direction F Ｄ The upper axial flow FA in the opposite direction to Ｕ ~FD Ｕ (Hereinafter, this will be collectively referred to as the upper axial flow F Ｕ The upper axial flow F Ｕ has a height component (upward component) moving away from the bottom 22 of the stirring vessel 2, and rises in the axial direction near the inner peripheral wall of the stirring vessel 2 or the baffle 4.

[0023] In order to realize a desirable circulation flow, which will be described later, in the stirred tank 2, the height dimension of the blades 33 (hereinafter simply referred to as the height) is made larger or smaller as the blade portion 31 approaches the bottom 22 of the stirred tank 2. Specifically, the height of the blades 33 is made smaller on the upstream side of the axial flow directly generated by the blades 33 and made larger on the downstream side. In the example of FIG. 1, the blades 33 are arranged to circulate the downward axial flow F Ｄ In order to directly generate the airflow, the upper blades 33 on the upstream side are formed to have a smaller height (for example, the uppermost blade 33A is the smallest), and the lower blades 33 on the downstream side are formed to have a larger height (for example, the lowermost blade 33D is the largest). Note that the heights and radial dimensions of the blades 33 of two blade portions 31 adjacent in the height direction may be equal to or different from each other.

[0024] In order to realize a desirable circulation flow, which will be described later, in the stirring tank 2, it is preferable that the ratio of the height of the shorter blade 33 to the height of the longer blade 33 between two vertically adjacent blades 31 be less than 0.8. Specifically, it is preferable that the ratio of the height of the shorter blade 33A to the height of the longer blade 33B between two vertically adjacent blades 31A and 31B be less than 0.8, it is preferable that the ratio of the height of the shorter blade 33B to the height of the longer blade 33C between two vertically adjacent blades 31B and 31C be less than 0.8, and it is preferable that the ratio of the height of the shorter blade 33C to the height of the longer blade 33D between two vertically adjacent blades 31C and 31D be less than 0.8.

[0025] The blades 31A to 31D may be arranged at approximately equal intervals along the height direction, or, as in the illustrated example, may be arranged at intervals h1 to h3 (hereinafter collectively referred to as intervals h) that may vary along the height direction. Each interval h1 to h3 may be adjusted to achieve a desired circulation flow, described below, within the stirred tank 2. For example, as described above, the height of the blades 33 may be increased closer to the bottom 22 of the stirred tank 2, and accordingly, the interval h along the height direction of each blade 31 may be increased closer to the bottom 22 of the stirred tank 2 (for example, h1≦h2≦h3).

[0026] Furthermore, in order to realize the desired circulation flow described later within the stirring tank 2, it is preferable that the heightwise distance (i.e., the interval h) between two vertically adjacent blade portions 31 is equal to or less than the blade diameter d of each blade portion 31 (h≦d).

[0027] FIG. 2 is a comparative example of the agitator 1 of FIG. 1. This agitator 1 differs from the agitator 1 of the present embodiment of FIG. 1 only in the configuration of the agitator blade 3. Specifically, in the agitator blade 3 of FIG. 2, the heights of the blades 33A to 33C provided on the multiple blade portions 31A to 31C are constant regardless of the height in the agitator tank 2. In addition, the number of blade portions 31 (3) in the agitator blade 3 of FIG. 2 is fewer than the number of blade portions 31 (4) in the agitator blade 3 of FIG. 1. Furthermore, in the agitator blade 3 of FIG. 2, the heightwise distance between two blade portions 31 adjacent in the heightwise direction (i.e., the intervals h1 and h2) is greater than the blade diameter d of each blade portion 31 (h>d).

[0028] 3 and 4 are flow patterns that visualize the flow of the fluid to be stirred in the stirring tank 2 for this embodiment (FIG. 1) and the comparative example (FIG. 2).

[0029] 4, which shows the flow pattern of the comparative example, an upper circulation flow PCF1 is formed, which passes through the upper blade portion 31A and partially circulates in the upper part of the agitation tank 2, and a lower circulation flow PCF2 is formed, which passes through the lower blade portions 31B and 31C and partially circulates in the lower part of the agitation tank 2. The circulation directions of the upper circulation flow PCF1 and the lower circulation flow PCF2 are opposite to each other. That is, near the rotation shaft 30 (inner peripheral side), the upper circulation flow PCF1 rises along the axial direction while the lower circulation flow PCF2 descends along the axial direction, and on the outer peripheral side of the agitation impeller 3, the upper circulation flow PCF1 descends along the axial direction while the lower circulation flow PCF2 rises along the axial direction.

[0030] In particular, on the outer periphery of the agitator blade 3, the descending upper circulation flow PCF1 and the ascending lower circulation flow PCF2 collide with each other with approximately the same strength, resulting in the formation of a flow partition wall W between the upper blade portion 31A and the lower blade portion 31B. As a result of the interior of the agitator vessel 2 being divided into upper and lower portions by the partition wall W, the agitation performance of the entire agitator 1 deteriorates. Furthermore, as a result of the agitated fluid remaining at the partition wall W, low-specific-gravity monomers and polymers tend to adhere to the inner circumferential wall of the agitator vessel 2 and the baffle 4 near the partition wall W.

[0031] As a result of our own investigation, we have determined that the main reason why the partition wall W is formed between the wing portions 31 is that the height of the blades 33 provided on each wing portion 31 is constant in the comparative example of Fig. 2. In other words, since the height of the upper blade 33A that mainly contributes to the formation of the upper circulation flow PCF1 and the height of the lower blades 33B and 33C that mainly contribute to the formation of the lower circulation flow PCF2 are equal, the upper circulation flow PCF1 and the lower circulation flow PCF2 compete with or collide with each other, resulting in the formation of the partition wall W.

[0032] Therefore, in the present embodiment shown in FIG. 1 , as described above, the height of the blades 33 is increased for blades 31 closer to the bottom 22 of the agitation tank 2. As a result, as shown in FIG. 3 , which shows the flow pattern of this embodiment, a circulation flow CF is formed that circulates throughout the agitation tank 2 through all of the blades 31A to 31D. It is believed that, as a result of reducing the height of the upper blade 33A, which formed the upper circulation flow PCF1 that competed with the lower circulation flow PCF2 in the comparative example ( FIG. 4 ), the weakened upper circulation flow PCF1 was absorbed (or swallowed) by the stronger lower circulation flow PCF2, forming a single large circulation flow CF. As described above, for two vertically adjacent blades 31, the ratio of the height of the shorter blade 33 to the height of the taller blade 33 is less than 0.8, the heightwise spacing h of each blade 31 is adjusted, and the heightwise spacing h of each blade 31 is set to be equal to or less than the blade diameter d of each blade 31. These factors also contribute to the realization of a desirable circulation flow CF.

[0033] This circulation flow CF descends axially from the top blade 31A to the bottom blade 31D near the rotating shaft 30 (inner peripheral side), and ascends axially from the bottom blade 31D to the top blade 31A on the outer peripheral side of the agitator impeller 3. In this way, the circulation flow CF circulates widely between the top and bottom of the vertically elongated agitator vessel 2, effectively mixing the agitated fluid in the agitator vessel 2 and homogenizing its concentration. The circulation flow CF also effectively agitates the agitated fluid through the blades 31A-31D, through which the circulation flow CF passes. As a result, the agitation performance of the agitator 1 as a whole is greatly improved. Furthermore, because the partition walls W, as in the comparative example ( FIG. 4 ), are not formed, the agitated fluid is less likely to stagnate between the blades 31, and therefore monomers and polymers are less likely to adhere to the inner peripheral wall of the agitator vessel 2 or the baffle 4. Furthermore, when the stirring device 1 is used for suspension polymerization accompanied by particle precipitation, the degree of uniformity of the monomer dispersed in the stirring tank 2 is increased, so that homogeneous particles with small particle size variations can be obtained.

[0034] Fig. 5 shows a schematic configuration of a stirring device 1 according to a modification of the first embodiment shown in Fig. 1. The same components as those in Fig. 1 are designated by the same reference numerals, and redundant explanations will be omitted. This stirring device 1 differs from the stirring device 1 according to the first embodiment shown in Fig. 1 only in the configuration of the stirring blades 3.

[0035] The blades 33 provided on each blade portion 31 of the agitating blade 3 rotate integrally with the rotating shaft 30 and the blade portion body 32 in the illustrated rotation direction R′ (counterclockwise direction in top view), thereby causing an upward axial flow FA of the agitated fluid having a height direction component (upward component) moving away from the bottom 22 of the agitating vessel 2. Ｕ ~FD Ｕ (Hereinafter, this will be collectively referred to as the upper axial flow F Ｕ (also referred to as

[0036] Upper axial flow F Ｕ The blade 33 that generates the upper axial flow F is provided on the radial center side of the mixing blade 3, i.e., on the rotating shaft 30 side. Ｕ On the other hand, on the radial outer periphery of the agitating blade 3, i.e., in the vicinity of the inner circumferential wall of the agitating vessel 2 or the baffle 4, the agitated fluid circulating or convecting in the agitating vessel 2 flows upward in the axial direction F Ｕ The downward axial flow FA in the opposite direction to Ｄ ~FD Ｄ (Hereinafter, this will be collectively referred to as the downward axial flow F Ｄ The downward axial flow F Ｄ has a vertical component (downward component) toward the bottom 22 of the stirring vessel 2 and descends in the axial direction near the inner peripheral wall of the stirring vessel 2 or the baffle 4.

[0037] In order to realize a desirable circulation flow CF (but in the opposite direction) in the stirring tank 2 similar to that in FIG. 3, the height of the blades 33 is made smaller on the upstream side of the axial flow directly generated by the blades 33 and made larger on the downstream side. In the example of FIG. 5, the blades 33 are formed so that the upper axial flow F Ｕ In order to directly generate the above-mentioned flow, the blades 33 on the upstream side are formed to have a smaller height (for example, the lowest blade 33D is the smallest), and the blades 33 on the downstream side are formed to have a larger height (for example, the top blade 33A is the largest).

[0038] 3 (but in the opposite direction) in the stirring tank 2, the ratio of the height of the narrower blade 33 to the height of the wider blade 33 between two vertically adjacent blades 31 is preferably less than 0.8. Specifically, the ratio of the height of the narrower blade 33B to the height of the wider blade 33A between two vertically adjacent blades 31A and 31B is preferably less than 0.8; the ratio of the height of the narrower blade 33C to the height of the wider blade 33B between two vertically adjacent blades 31B and 31C is preferably less than 0.8; and the ratio of the height of the narrower blade 33D to the height of the wider blade 33C between two vertically adjacent blades 31C and 31D is preferably less than 0.8.

[0039] The blades 31A-31D may be arranged at substantially equal intervals along the height direction, or, as shown in the illustrated example, may be arranged at intervals h1-h3 (hereinafter collectively referred to as intervals h) that may vary along the height direction. The intervals h1-h3 may be adjusted to achieve a desired circulation flow CF (similar to that shown in FIG. 3 ) within the stirred tank 2 (but in the opposite direction). For example, as described above, the height of the blades 33 may be reduced as the blades are closer to the bottom 22 of the stirred tank 2, and accordingly, the interval h along the height direction of each blade 31 may be reduced as the blades are closer to the bottom 22 of the stirred tank 2 (e.g., h1 ≧ h2 ≧ h3).

[0040] In order to realize a desirable circulation flow CF similar to that shown in FIG. 3 (but in the opposite direction) in the stirring tank 2, it is preferable that the heightwise distance (i.e., the interval h) between two vertically adjacent blade portions 31 is equal to or less than the blade diameter d of each blade portion 31 (h≦d).

[0041] The agitator 1 of FIG. 5 can achieve a desirable circulation flow CF (although in the opposite direction) within the agitator vessel 2, similar to that of FIG. 3 . This circulation flow CF (not shown) ascends axially from the lowest blade 31D toward the highest blade 31A near the rotating shaft 30 (inner periphery), and descends axially from the highest blade 31A toward the lowest blade 31D toward the outer periphery of the agitator impeller 3. In this way, the circulation flow CF circulates widely between the top and bottom of the vertically elongated agitator vessel 2, effectively mixing the agitated fluid within the agitator vessel 2 and homogenizing its concentration. Furthermore, the circulation flow CF is effectively agitated by the blades 31A-31D, through which it passes sequentially. As a result, the agitation performance of the agitator vessel 1 as a whole is greatly improved. Furthermore, because the partition wall W, as in the comparative example ( FIG. 4 ), is not formed, the agitated fluid is less likely to stagnate between the blades 31, making it less likely for monomers or polymers to adhere to the inner periphery of the agitator vessel 2 or the baffle 4.

[0042] The present disclosure has been described above based on the embodiments. Various modifications are possible to the combinations of the components and processes in the exemplary embodiments, and it will be obvious to those skilled in the art that such modifications are included within the scope of the present disclosure.

[0043] Although the first embodiment ( FIG. 1 ) illustrates the blades 33 that generate an axial flow, blades 33 that generate an axial flow and blades 33 that generate a radial flow may be combined (interwoven). For example, a blade section 31 having a blade 33 that generates an axial flow and a blade section 31 having a blade 33 that generates a radial flow may be provided on the same agitator 3. Furthermore, at least one blade section 31 may be provided with both a blade 33 that generates an axial flow and a blade 33 that generates a radial flow. Furthermore, at least one blade 33 in at least one blade section 31 may be capable of simultaneously generating both an axial flow and a radial flow. Even in such a modified example, it is preferable that the height of the blades 33 be greater or smaller as the blade section 31 is closer to the bottom 22 of the agitator 2.

[0044] The configuration, operation, and function of each device and method described in the embodiments can be realized by hardware resources, software resources, or a combination of hardware and software resources. Examples of hardware resources include processors, ROM, RAM, and various integrated circuits. Examples of software resources include operating systems, applications, and other programs.

[0045] The present disclosure relates to a stirring device and the like.

[0046] 1 Stirring device, 2 Stirring tank, 3 Stirring blade, 21 Straight body portion, 22 Bottom portion, 30 Rotating shaft, 31 Blade portion, 33 Blade.

Claims

1. A stirring device equipped with a stirring blade that stirs a stirred fluid contained in a stirring tank by rotation, wherein the stirring blade has a plurality of blade portions that are arranged at a distance in the height direction of the stirring tank, each of the blade portions has a blade that generates a flow of the stirred fluid having a height direction component of the stirring tank by rotation, and the height direction dimension of the blade is larger or smaller the blade portion that is closer to the bottom of the stirring tank.

2. The stirring device described in claim 1, wherein the blades in each wing portion rotate to generate a flow of the stirred fluid having a height component toward the bottom of the stirring tank, and the height dimension of the blade is larger for the wing portion closer to the bottom of the stirring tank.

3. The stirring device described in claim 1, wherein the blades in each blade portion generate a flow of the stirred fluid having a height component that moves away from the bottom of the stirring tank by rotation, and the height dimension of the blade is smaller for the blade portion closer to the bottom of the stirring tank.

4. The stirring device according to claim 1, wherein the blades in each of the blade portions generate a flow of the stirred fluid having a radial component of the stirring vessel by rotation.

5. A stirring device as described in any one of claims 1 to 4, wherein for two adjacent blade portions in the vertical direction, the ratio of the height dimension of the blade having the smaller height dimension to the blade having the larger height dimension is less than 0.

8.

6. A mixing device as described in any one of claims 1 to 4, wherein the heightwise distance between two adjacent blade portions in the height direction is equal to or less than the radial blade diameter of each blade portion in the stirring tank.

7. A stirring device described in any one of claims 1 to 4, wherein the ratio L / D of the liquid level height L of the stirred fluid in the stirring tank in the vertical direction to the tank diameter D in the radial direction of the stirring tank is 1.2 or more.

8. A stirring device as described in any one of claims 1 to 4, wherein the stirring blade has three or more blade portions arranged at a distance from each other in the vertical direction.

9. The stirring device according to any one of claims 1 to 4, wherein the stirred fluid contains a medium and a monomer, and polymerization of the monomer is promoted by stirring with the rotating stirring blades.

10. A stirring method in a stirring device equipped with a stirring blade that stirs a stirred fluid contained in a stirring tank by rotation, wherein the stirring blade has a plurality of blade portions arranged at a distance in the height direction of the stirring tank, the blade portions having blades with larger or smaller height dimensions the closer they are to the bottom of the stirring tank, and the stirring method generates a flow of the stirred fluid having a height direction component of the stirring tank by rotation of each of the blades.

Images