Agitation tank and stirring method

Abstract

To improve performance in diffusing an additive in a stirring tank equipped with a baffle.SOLUTION: A stirring tank is provided with a tank main body comprising a bottom part and a side wall part erected in a cylindrical shape from an outer periphery of the bottom part, a baffle provided to extend in a vertical direction inside the side wall part, a stirring device that generates swirl flow in liquid in the tank, inside the tank main body, and a dripping device that drips an additive that is added to the liquid in the tank. The baffle and the dripping device are arranged so that the liquid in the tank flowing as the swirl flow reaches a position where the baffle is arranged. at the time when the liquid moves at 90 degrees or more and less than 330 degrees from a position on which the additive is dripped.SELECTED DRAWING: Figure 1

Description

[Technical Field]

[0001] The present invention relates to a stirring tank, and more particularly to a stirring tank comprising a tank body and a stirring device that generates a swirling flow in the liquid inside the tank body. [Background technology]

[0002] Conventionally, agitated tanks, which stir the liquid contained within a bottomed cylindrical tank body, have been used for various purposes. Known agitated tanks of this type include a stirring device in addition to the tank body, configured such that a swirling flow is formed inside the tank body by the stirring device.

[0003] The stirred tanks described above are also used in chemical reactions in the manufacture of pharmaceuticals. In chemical reactions using stirred tanks, chemicals and other substances are added to the liquid inside the tank as additives, and the additives are mixed while stirring the liquid inside the tank. Chemical reactions carried out in this way include not only reactions between chemicals, but also reactions in which solutes dissolved in the liquid inside the tank are crystallized using a poor solvent (see Patent Document 1 below). For this reason, not only chemicals but also organic solvents and water are widely used as additives added to the liquid inside the tank. [Prior art documents] [Patent Documents]

[0004] [Patent Document 1] Japanese Patent Publication No. 2005-35970 [Overview of the project] [Problems that the invention aims to solve]

[0005] In situations where additives are added to a liquid in a stirred tank, it is desirable that the additives quickly diffuse throughout the liquid to quickly eliminate variations in additive concentration. Adding additives to a liquid in a stirred tank is done not only in the pharmaceutical industry but also in a wide range of fields such as electronic materials and fine chemicals. The rapid diffusion of additives into the liquid is a common requirement for stirred tanks used in various fields, not just specific ones. For this reason, stirred tanks equipped with baffles to disrupt the flow of the liquid are sometimes used. However, even with baffles, it is difficult to sufficiently improve the diffusivity of additives, and the above requirements are not fully met. Therefore, the present invention aims to improve the diffusivity of additives in a stirred tank equipped with baffles. [Means for solving the problem]

[0006] In order to solve the above problems, the inventors conducted diligent research and discovered that the diffusivity of the additive can be improved by setting the position where the additive is dropped into the liquid in the tank to a specific position relative to the baffle. To solve the above problems, the present invention provides: A tank body comprising a bottom and side walls that rise cylindrically from the outer circumference of the bottom, A baffle is provided on the inner side of the aforementioned side wall portion so as to extend vertically, A stirring device inside the tank body generates a swirling flow in the liquid inside the tank, The tank is equipped with a dropping device for dropping additives to be added to the liquid inside the tank, The present invention provides an agitated tank in which the baffle and the dropping device are arranged such that the liquid in the tank, which is flowing in a swirling flow, reaches the position where the baffle is provided when it has moved 90 degrees or more but less than 330 degrees from the position where the additive was dropped. [Effects of the Invention]

[0007] According to the present invention, a stirring tank capable of improving the diffusivity of additives can be provided. [Brief explanation of the drawing]

[0008] [Figure 1] Figure 1 is a schematic front view showing a stirring tank. [Figure 2] Figure 2 is a schematic side view showing an example of a piping section of a dropping device. [Figure 3] Figure 3 is a schematic front view showing a stirring tank provided with baffles different from those in Figure 1. [Figure 4] Figure 4 is a cross-sectional view taken along the line IV-IV in Figure 1. [Figure 5] Figure 5 is a schematic diagram of an experimental apparatus used for PIV measurement in the examples. [Figure 6] Figure 6 is a schematic diagram (plan view) showing the positional relationship between the injection position of the tracer and the baffle in PIV measurement. [Figure 7] Figure 7 is a diagram showing PIV results and CFD results for the vertical flow velocity in the stirring tank. [Figure 8] Figure 8 is a diagram representing the analysis results of the mixing and dispersion process by CFD. [Figure 9A] Figure 9A is a diagram showing the transition of the maximum concentration value of the tracer in the stirring tank for each injection position of the tracer. [Figure 9B] Figure 9B is a diagram showing the transition of the volume of the region where the tracer concentration is 0.1 wt% or more. [Figure 10A] Figure 10A is a diagram showing the transition of the maximum concentration value of the tracer in the stirring tank for each type of stirring blade. [Figure 10B] Figure 10B is a diagram showing the transition of the volume of the region where the tracer concentration is 0.1 wt% or more.

Embodiments for Carrying Out the Invention

[0009] An embodiment of the present invention will be described below with reference to the figures. In the following description, the stirring tank will be explained using as an example a case in which the final product substance or intermediate particles are produced by a poor solvent crystallization method in a particle manufacturing facility. However, the stirring tank of this embodiment is not limited to such a specific use and can be used for various purposes. Figure 1 is a schematic front view showing the particle manufacturing facility 100 in this embodiment. As shown in the figure, the particle manufacturing facility 100 comprises a stirring tank 1 and an additive tank 5 containing additive AF to be supplied to the stirring tank 1.

[0010] The stirring tank 1 of this embodiment comprises a tank body 10, a dripping device 20, a stirring device 30, and a baffle 40. The additive tank 5 of this embodiment comprises a storage tank 51 for storing additive AF, an additive supply pipe 52 for supplying additive AF from the storage tank 51 to the dripping device 20 of the stirring tank 1, and a flow rate adjustment valve 53 for adjusting the flow rate of additive AF in the additive supply pipe 52.

[0011] In this embodiment, the tank body 10 of the stirring tank 1 can be made of, for example, glass lining. The tank body 10 of this embodiment may be made of metal such as stainless steel, glass, or plastic. The tank body 10 comprises a bottom portion 12 which is circular in plan view, a side wall portion 13 which extends upward in a cylindrical shape from the outer peripheral edge of the bottom portion 12, and a top portion 14 which is circular in plan view and is positioned opposite the bottom portion 12 in the vertical direction and closes the upper end of the side wall portion 13. The tank body 10 of this embodiment further comprises a cylindrical portion 11 which extends upward in a short cylindrical shape from the top portion 14. The tank body 10 of this embodiment is positioned such that the central axis 10ax of the cylindrical side wall portion 13 is in the vertical direction.

[0012] The tank body 10 in this embodiment has a storage space 10c enclosed by the bottom 12, the side wall 13, and the ceiling 14, and is configured to accommodate the tank liquid TF in the storage space 10c.

[0013] The tank body 10 in this embodiment is not particularly limited in terms of size in the length and width directions, but for example, it may have a diameter (inner diameter: D) of 0.4 m or more. The diameter of the tank body 10 may be 0.6 m or more, 0.8 m or more, or 1.0 m or more. The diameter of the tank body 10 may be 1.2 m or more, 1.5 m or more, or 1.8 m or more. The diameter (D) of the tank body 10 can be, for example, 4.0 m or less. The diameter of the tank body 10 may be 3.0 m or less, or 2.7 m or less. The diameter of the tank body 10 may be 2.5 m or less, or 2.2 m or less.

[0014] The tank body 10 can be made to a height that allows the liquid TF inside the tank to be contained in the containment space 10c with a liquid depth of 0.5 times or more the diameter (D) of the tank body 10. The tank body 10 may also be capable of forming a liquid depth of 0.6 times (0.6·D) or more the diameter (D), or it may be capable of forming a liquid depth of 0.7 times (0.7·D) or more the diameter (D). The tank body 10 may also be capable of forming a liquid depth of 0.8 times (0.8·D) the diameter (D). B It may be possible to form a liquid depth of 0.9 times (0.9·D) or more. The dimensions of the containment space 10c in the direction of the central axis 10ax (vertical direction) may be 0.6 times (0.6·D) or more of the diameter (D), 0.7 times (0.7·D) or more, 0.8 times (0.8·D) or more, or 0.9 times (0.9·D) or more. The dimensions of the containment space 10c in the tank body 10 in the direction of the central axis 10ax are, for example, 2.0 times (2.0·D) or less of the diameter (D). The dimensions of the containment space 10c in the tank body 10 in the direction of the central axis 10ax may be 1.5 times (1.5·D) or less of the diameter (D).

[0015] The liquid TF in the tank in this embodiment can be, for example, a solution in which the compound to be crystallized and the impurities to be removed are dissolved in a good solvent that exhibits good solubility for both. On the other hand, the additive AF can be a poor solvent that is poorly soluble in the compound and exhibits higher solubility for the impurities than for the compound.

[0016] The tank body 10 has four openings in the ceiling portion 14 that communicate with the containment space 10c. One of the four openings is a manhole (not shown) fitted with a cover that has a viewing window made of a glass plate. One of the remaining three openings is a dripping device mounting port 14a for attaching the dripping device 20. The remaining two are a stirring device mounting port 14b and a baffle mounting port 14c for attaching the stirring device 30 and baffle 40, respectively.

[0017] The agitator mounting port 14b is located approximately in the center of the ceiling portion 14. The dripping device mounting port 14a and the baffle mounting port 14c are located on the left and right sides of the ceiling portion 14, with the agitator mounting port 14b in between. The tank body 10 further comprises cylindrical portions 11 that extend upward from each of the dripping device mounting port 14a, the agitator mounting port 14b, and the baffle mounting port 14c. More specifically, the tank body 10 comprises a first cylindrical portion 11a extending from the dripping device mounting port 14a, a second cylindrical portion 11b extending from the agitator mounting port 14b, and a third cylindrical portion 11c extending from the baffle mounting port 14c.

[0018] Each of the first cylindrical portion 11a, the second cylindrical portion 11b, and the third cylindrical portion 11c is fitted with a cover 15, similar to the manhole described above (not shown). The cover 15 is fitted above the cylindrical portion 11 so as to close the opening at the upper edge of each cylindrical portion.

[0019] In this embodiment, the stirring tank 1 is not equipped with a pump or the like for transporting the additive AF in the dripping device 20. In this embodiment, the storage tank 51 of the additive tank 5 is positioned above the tank body 10 of the stirring tank 1, and the stirring tank 1 and the additive tank 5 are arranged so that the additive AF flows naturally down to the tank body 10 through the additive supply pipe 52 due to the action of gravity. The particle manufacturing equipment 100 is configured so that the amount of additive AF supplied to the tank body 10 per unit time (for example, per minute) can be adjusted by a flow rate control valve 53. For example, a plunger valve, a ball valve, or a butterfly valve can be used as the flow rate control valve 53. The amount of additive AF supplied to the tank body 10 per unit time may be limited to a range of, for example, -20% to +20% with respect to the average value over the entire period during which the additive AF is supplied. The range of variation may also be within the range of -10% to +10%, -5% to +5%, or -2% to +2%.

[0020] In the stirring tank 1 of this embodiment, the dropping device 20 may be equipped with a metering pump or the like to ensure more reliable quantitative supply of the additive AF as described above. More specifically, the dropping device 20 may have a magnetic pump or the like installed in front of the tank body 10 (upstream in the direction of additive AF supply), and may be configured so that the amount of additive AF supplied to the tank body 10 per unit time can be controlled by the magnetic pump.

[0021] In the stirring tank 1 of this embodiment, it is preferable that the additive AF is dropped into the liquid TF inside the tank while controlling the supply amount as described above. It is preferable that the additive AF is dropped into the liquid TF inside the tank over a certain period of time (for example, 10 minutes or more) after the liquid TF inside the tank has been contained in the containment space 10c and the flow state of the liquid TF inside the tank has stabilized by the stirring device 30.

[0022] The dripping device 20 of this embodiment includes a vertical piping section 211 extending vertically through approximately the center of the first cylindrical section 11a as a piping section 21 for introducing the additive AF into the containment space 10c. The dripping device 20 may be configured to drip the additive AF from the vertical piping section 211 with the lower end of the vertical piping section 211 as an open end, with the open end positioned above the water surface of the liquid TF in the tank. The dripping device 20 of this embodiment may further include a horizontal piping section 212 connected to the lower end of the vertical piping section 211 and extending approximately horizontally from the connection point, as shown in Figure 2, for example. The end of the horizontal piping section 22 on the side opposite to the side connected to the vertical piping section 211 may be provided with a discharge port for dripping the additive AF toward the water surface of the liquid TF in the tank.

[0023] In this embodiment, the dropping device 20 may have, for example, variable lengths for the vertical piping section 211 and the horizontal piping section 212, allowing the vertical and horizontal positions of the discharge port to be freely changed. Furthermore, the dropping device 20 may have multiple piping sections 21 that can be arranged in the first cylindrical section 11a and have different lengths for the vertical piping section 211 and the horizontal piping section 212, allowing the piping section 21 to be replaced according to the dropping position of the additive AF. That is, the dropping device 20 in this embodiment may be configured to allow adjustment of the dropping position of the additive AF. In this embodiment, the lid 15 is attached to the first cylindrical section 11a to seal the gap between the first cylindrical section 11a and the vertical piping section 211. In this embodiment, however, the lid 15 may not be attached to the first cylindrical section 11a, leaving the gap open in order to observe the crystallization state through it.

[0024] In this embodiment, the stirring tank 1 may have multiple cylindrical sections (dropping device mounting ports) on the tank body 10, similar to the first cylindrical section 11a, to which the dropping device 20 can be attached, thereby allowing adjustment of the position at which the additive AF is dropped.

[0025] In the stirring tank 1 of this embodiment, the dropping speed of the additive AF by the dropping device 20 can be, for example, 0.1 m / s or more, and may be 0.12 m / s or more, or even 0.15 m / s or more. Further, the dropping speed can be 20 m / s or less, 15 m / s or less, or even 12 m / s or less. The area of the opening at the end of the dropping device 20 for dropping the additive toward the liquid surface is "S: m 2 ", and when the amount (average flow rate) of the additive dropped passing through the opening per unit time is "V: m 3 / s", the dropping speed (v: m / s) can be obtained as a value (v = V / S) obtained by dividing the average flow rate (V) by the area (S).

[0026] When the discharge flow rate at the stirring blade 32 is "q d (m 3 / s)", it is preferable that the average flow rate (V) of the additive dropped per unit time by the dropping device 20 has a relationship satisfying the following formula (A1) with the discharge flow rate (q<00000%06>). It is more preferable that the average flow rate (V) has a relationship satisfying the formula (A2) with the discharge flow rate (q d ), and it is even more preferable that it has a relationship satisfying the formula (A3). Incidentally, the discharge flow rate (q d ) can be calculated, for example, from the blade shape or the like, and can be obtained by performing an analysis by a flow-follower method or the like. V ≦ 1200·q d ···(A1) V ≦ 1100·q d ···(A2) V ≦ 1000·q d ···(A3)

[0027] The stirring device 30 of this embodiment includes a rotating shaft 31 that extends in the vertical direction and is rotatably provided around the axis, a stirring blade 32 fixed to the rotating shaft 31, and a power machine (not shown) that applies rotational power to the rotating shaft 31. The stirring device 30 is used to promote the movement of the liquid TF in the tank in the direction of orbiting around the central axis 10ax to form a swirling flow SF by the liquid TF in the tank body 10.

[0028] The rotating shaft 31 extends vertically through the center of the second cylindrical portion 11b, penetrates the lid 15 mounted above the second cylindrical portion 11b, and extends above the lid 15. In this embodiment, the rotating shaft 31 extends vertically along the central axis 10ax of the tank body 10. The rotating shaft 31 extends downward through the agitator mounting port 14b and extends downward to just before reaching the bottom 12 of the tank body 10. In this embodiment, the stirring blade 32 is composed of a plurality of blades (stirring blades) mounted on the lower side of the rotating shaft 31. In this embodiment, at least some of the blades are located below the center of the housing space 10c in the height direction. That is, the stirring blade 32 is provided so as to impart kinetic energy to the tank liquid TF at least below the housing space 10c. The stirring blade 32 may be, for example, a three-bladed retractable blade. The three-bladed swept-back wing has three blades that extend radially from the lower end of the rotation axis 31, and each blade is curved so as it moves radially away from the rotation axis 31 and outward, it moves backward relative to the rotation direction of the rotation axis 31. In other words, in the three-bladed swept-back wing, the shape of each blade when viewed from above is curved and swept back.

[0029] The stirring blade 32 may be a paddle blade having two blades. The stirring blade 32 may also be a wide paddle blade, where the vertical dimension is greater than the dimension from the rotation axis 31 to the radially outer end. The stirring blade 32 may be a commercially available product, for example, sold by Kobe Steel Environmental Solutions Co., Ltd. under the product names "Twin Star" and "Full Zone".

[0030] The stirring device 30 of this embodiment may, if necessary, not have a rotating shaft 31 or stirring blades 32, and may be one that sucks in the liquid TF inside the tank at the bottom 12 or side wall 13 of the tank body 10 and blows out the sucked-in liquid TF in a direction that circulates around the central axis 10ax to form a swirling flow SF in the liquid TF inside the tank.

[0031] In this embodiment, as described above, the additive AF is dropped onto the surface of the liquid TF in the tank. To quickly diffuse the dropped additive AF into the liquid TF in the tank, it is preferable to generate a vertical circulating flow CF consisting of downward and upward flows in addition to the swirling flow SF. When an agitator 32 is used, which has blades that are retracted on the radially outer side relative to the direction of rotation, the liquid TF in the tank that hits the blades is pushed radially outward when the rotating shaft 31 is rotated, and as a result, a vertical circulating flow CF consisting of a downward flow along the rotating shaft 31 and an upward flow along the side wall portion 13 is easily generated. Therefore, in this embodiment, it is preferable to use an agitator 32 having blades that are retracted on the radially outer side. Furthermore, it is preferable that the blades that are retracted on the radially outer side are located at the bottom of the containment space 10c.

[0032] In the stirred tank 1 of this embodiment, the stirring speed of the liquid TF in the tank by the stirring device 30 can be set to, for example, 50 rpm or more and 300 rpm or less for paddle blades or three-blade retracted blades. The stirring speed for paddle blades may be 100 rpm or more, or 150 rpm or more. The stirring speed for paddle blades may be 200 rpm or less. For three-blade retracted blades, the stirring speed may be 100 rpm or more, 150 rpm or more, or even 200 rpm or more. The stirring speed for three-blade retracted blades may be 250 rpm or less. When using wide paddle blades, the rotation speed may be 30 rpm or more, or even 50 rpm or more. When using wide paddle blades, the rotation speed may be 100 rpm or less, or even 80 rpm or less. The stirring power value per unit volume (Pv value) of the stirring device 30 is, for example, 0.05 (kW / m 3 ) or more. The Pv value is 0.1 (kW / m 3 It may be 0.2 (kW / m²) or more, and 3 ) or higher is also acceptable. The Pv value is, for example, 1.5 (kW / m³). 3 ) or less. The Pv value is 1.2 (kW / m 3 ) may be less than or equal to 1.0 (kW / m 3 The following are also acceptable:

[0033] Let "n(1 / s)" be the rotation speed of the stirring blade 32 per second, and "t" be the mixing time by the stirring blade 32. M When (s) is the product of these, the dimensionless mixing time (nt M ) can be set by the following formula:

[0034]

number

[0035] The variables in the above formula are as follows: nt M :Dimensionless mixing time (-) d: Blade diameter (m) D: Tank diameter (m) N qd :Discharge flow rate (-) N p :Number of power(-)

[0036] Note that the number of discharge flow rates (N) in the above formula qd ) can be calculated using the following formula.

number

[0037] The variables in the above formula are as follows: q d :Discharge flow rate (m 3 / s) n: rotational speed (1 / s) d: Blade diameter (m)

[0038] In the stirring tank 1 of this embodiment, for example, the discharge flow rate (N qd The value of ) may be set to any value within the range of 3.5 to 4.5, and the shape of the stirring blade 32 and the tank body 10, as well as the operating method such as the rotation speed and power output, may be adjusted to satisfy the above formula.

[0039] In this embodiment, the baffle 40 is fixed at its upper end to the lid 15 and extends downward from the lid 15 through the central part of the third cylindrical portion 11c. In this embodiment, the baffle 40 is positioned inward from the side wall portion 13, with a gap between it and the side wall portion 13 so that it does not come into contact with the side wall portion 13. The lower end of the baffle 40 is also positioned so that it does not come into contact with the bottom portion 12 of the tank body 10. In other words, the baffle 40 is suspended from the ceiling portion 14 of the tank body 10.

[0040] The baffle 40 of this embodiment has a shape formed by compressing a pipe with its ends closed in the diameter direction to flatten it, and is a so-called beaver tail shape. The baffle 40 of this embodiment has an oval cross-sectional shape when cut by a plane perpendicular to the length direction, and the oval shape has a direction that is the minor axis (minor axis direction) and a direction that is the major axis (major axis direction), and the minor axis direction and the major axis direction are perpendicular to each other. The baffle 40 of this embodiment is arranged such that the major axis direction is along the radial direction of the tank body 10 and the minor axis direction is the circumferential direction of the tank body 10.

[0041] In this embodiment, the baffle 40 may not be beavertail-shaped, but rather a long plate-shaped baffle as shown in Figure 3. Furthermore, the baffle 40 does not necessarily have to be suspended from the ceiling portion 14 as shown in Figure 1; it may be supported by a support member 41 provided to protrude radially inward from the inner wall surface of the side wall portion 13, as shown in Figure 3. The long plate-shaped baffle 40 is arranged such that its longitudinal direction is vertical and its thickness direction is circumferential to the tank body 10, similar to the beavertail-shaped baffle. The long plate-shaped baffle 40 can also be arranged with a gap between it and the inner wall surface of the side wall portion 13, similar to the beavertail-shaped baffle 40.

[0042] If the liquid depth TF in the tank in a stationary state is defined as "L0", and the vertical length of the baffle 40 in the portion immersed in the liquid TF is defined as "L1", then the ratio of the length of the baffle 40 (L1) to the liquid depth (L0) (L1 / L0) can be, for example, 0.6 or more, 0.65 or more, or even 0.7 or more. Furthermore, the baffle 40 may be arranged so that the ratio (L1 / L0) is 0.9 or less, or 0.8 or less. By immersing the baffle in the liquid at a predetermined ratio or more, the rotation of the material to be processed in the tank is suppressed and stirring is promoted, thereby improving the diffusibility of the material to be processed.

[0043] If the tank diameter (diameter of the containment space 10c) is "D(m)", the distance from the central axis 10ax to the radial center of the baffle 40 is "R(m)", and the gap dimension between the baffle 40 and the inner wall surface of the side wall portion 13 in the radial direction is "G(m)", then the baffle 40 is arranged such that, for example, if the stirring blade 32 is a paddle blade or a three-bladed swept blade, it satisfies the following equations (B) and (C). 0.25·D ≤ R ···(B) 0.02·D ≤ G ···(C) The dimension (G) of the gap between the baffle 40 and the inner wall surface of the side wall 13 in the radial direction of the tank body 10 can be, for example, 0.01 m or more and 0.1 m or less. The dimension of the gap may be 0.02 m or more, or 0.05 m or less. On the front side of the baffle 40 in the direction of the swirling flow SF, the liquid TF inside the tank is under positive pressure. On the other hand, on the rear side of the baffle 40 in the direction of the swirling flow SF, a negative pressure state is created, making it easier for the liquid TF inside the tank to stagnate. By providing a gap between the baffle 40 and the inner wall surface of the side wall 13, the magnitude of the negative pressure and the size of the area where negative pressure occurs can be reduced, making it easier to achieve good agitation.

[0044] In this embodiment, the tank body 10 does not need to have a single baffle 40; multiple baffles 40 may be provided. In this embodiment, it is preferable to have only one baffle 40.

[0045] In this embodiment, the baffle 40 in the tank body 10 and the dripping device 20 are arranged such that the position of the baffle 40 and the dripping position of the additive AF are in a specific relationship. In this embodiment, the baffle 40 and the dripping device 20 are arranged such that the liquid TF in the tank, which is flowing as a swirling flow SF, reaches the position where the baffle 40 is located when it has moved 90 degrees or more but less than 330 degrees from the position where the additive AF is dropped. In this embodiment, as shown in Figure 4, the angle θ between the position where the baffle 40 is located and the dripping position of the additive AF is 180 degrees.

[0046] The angle from the dropping position of additive AF to the position of baffle 40 can be determined by first finding the center point (the centroid of the contour shape of the range VA1) of the liquid surface TF in the tank where additive AF is dropped, and setting this center point as a virtual point VP1 indicating the dropping position of additive AF. Furthermore, the angle θ can be determined by setting a virtual line (first virtual line VL1) passing through the central axis 10ax of the tank body 10 and the center point of baffle 40, and a virtual line (second virtual line VL2) passing through the central axis 10ax and virtual point VP1. That is, the angle θ can be determined as the angle between the first virtual line VL1 and the second virtual line in the horizontal plane passing through virtual point VP1 (the value obtained by finding the angle from the second virtual line VL2 to the first virtual line VL1 in the direction of the swirling flow SF).

[0047] In this embodiment, the angle θ between the first virtual line VL1 and the second virtual line VL2 is, for example, 90 degrees or more and less than 330 degrees. The lower limit of the angle θ may exceed 90 degrees. The angle θ may be 100 degrees or more, 120 degrees or more, 150 degrees or more, 180 degrees or more, or exceed 180 degrees. The upper limit of the angle θ may be 310 degrees or less. The angle θ may be 290 degrees or less, or 270 degrees or less.

[0048] The dropping position of additive AF can be, for example, the position reached when the swirling flow, having passed the location where the baffle 40 is provided, has moved 30 degrees or more. The dropping position of additive AF may also be the position reached when the swirling flow, having passed the location where the baffle 40 is provided, has moved 50 degrees or more, or it may be the position reached when it has moved 70 degrees or more, or it may be the position reached when it has moved 90 degrees or more. The dropping position of additive AF may also be the position reached when the swirling flow has moved 100 degrees or more, or it may be the position reached when it has moved 130 degrees or more.

[0049] The baffle 40 is provided to disrupt the flow of the liquid TF inside the tank and improve the agitation of the liquid TF. Additive AF, dropped onto the surface of the liquid TF inside the tank, spreads within the liquid TF over time due to Brownian motion, even when the liquid TF is left standing. In this embodiment, when the additive AF has spread to an appropriate extent, the flow of the liquid TF inside the tank is disrupted by the baffle 40, causing the additive AF to diffuse more quickly over a wider area, thus eliminating concentration variations in the liquid TF inside the tank at an early stage.

[0050] In this embodiment, it is preferable that the following relational expression (1) is satisfied when the radial dimension of the baffle 40 is "W (m)", the distance from the radial outer edge of the baffle 40 to the side wall portion 13 is "G (m)", and the radial distance from the virtual point VP1 (additive dropping position) to the side wall portion 13 is "T (m)". G≦T≦[1.2×(G+W)] ···(1) In this embodiment, it is more preferable that the following relational expression (2) is satisfied. G≦T≦[1.1×(G+W)] ···(2) In this embodiment, it is preferable that the baffle 40 and the dispensing device 20 are arranged such that the dispensing position of the additive AF and the installation position of the baffle 40 are located on a single circumference centered on the central axis 10ax.

[0051] The baffle 40 and the dripping device 20 may be arranged to satisfy "(1.1×G)≦T≦[1.2×(G+W)] ···(3)", "(1.1×G)≦T≦[1.1×(G+W)] ···(4)", or "(1.1×G)≦T≦(G+W) ···(5)".

[0052] As described above, by positioning the dropping device 20 and the baffle 40 in an appropriate relative position, the additive AF can be diffused quickly, and variations in concentration in the tank liquid TF can be suppressed. In poor solvent crystallization, if the dropped poor solvent does not disperse quickly in the tank liquid, and areas where the poor solvent is present at a high concentration occur, scale can be generated or the purity of the precipitated particles can decrease. Therefore, it is preferable to use the stirring tank 1 of this embodiment.

[0053] Furthermore, the stirring tank 1 of this embodiment can be suitably used not only for poor-solvent crystallization but also for reaction crystallization and the like. When precipitating particles in the stirring tank 1 of this embodiment, the particles may be other than crystalline compounds or chemical substances. Specifically, the stirring tank 1 of this embodiment can be suitably used for poor-solvent precipitation and reaction precipitation of inorganic particles in the sol-gel method. Moreover, the stirring tank 1 of this embodiment can be applied to any reaction that produces fine particles by adding additives, and can be applied to polymerization reactions such as those that generate polymer compounds by dropwise adding monomers into a predetermined solution. The stirring tank 1 of this embodiment can be used for reactions by dropwise adding of trace components or reactions by adding highly active catalysts.

[0054] In the particle production method using the stirring tank 1 of this embodiment, A tank body 10 comprising a bottom portion 12 and a side wall portion 13 that rises cylindrically from the outer circumference of the bottom portion 12, A baffle 40 is provided on the inside of the side wall portion 13 so as to extend in the vertical direction, A stirring tank 1 is used, which is equipped with a stirring device 30 that generates a swirling flow SF in the liquid TF contained in the tank body 10, and a precipitation step is performed in which an additive AF is added to the liquid TF in the tank that is flowing with the swirling flow SF generated, causing particles to precipitate in the liquid in the tank. In the precipitation step, a particle production method can be employed in which the additive AF is dropped at a point that is 90 degrees or more but less than 330 degrees upstream from the position where the baffle is provided.

[0055] The additive AF may be dropped at a position 90 to 270 degrees upstream from the location where the baffle is provided. The additive AF may be dropped at a position greater than 90 degrees and less than or equal to 270 degrees upstream from the location where the baffle is provided. The additive AF may be dropped at a position concentric with the location where the baffle is provided.

[0056] When adding the additive AF, the additive AF may be continuously added to the liquid TF in the tank while controlling the amount added per unit time. When adding the additive AF, it is not necessary to add the additive AF continuously until the addition is complete; a supply period in which the additive AF is supplied to the liquid TF in the tank and a pause period in which the supply of the additive AF to the liquid TF in the tank are stopped may be alternated.

[0057] The addition of additive AF may be carried out after determining the total amount of additive AF necessary for optimal crystallization through preliminary experiments or other means. If the total amount of additive AF to be added is predictable, the addition of additive AF may be stopped before the predicted total amount is reached, and the remaining amount may be added while checking the crystallization state.

[0058] When adding the additive AF dropwise, a plurality of supply periods may be provided, including a first supply period and a second supply period provided after the first supply period, and a rest period may be provided between the first and second supply periods, such that the amount of additive AF added during the first supply period is greater than the amount added during the second supply period. In this case, the amount of additive AF added during the first supply period may be 50% by mass or more of the total amount of additive AF added, or 75% by mass or more. For example, the amount of additive AF added during the first supply period may be 99% or less of the total amount.

[0059] The dripping of additive AF onto the baffle 40 from a specific position may, for example, be performed only during the first supply period, and the dripping during the second supply period may be performed at a different location than during the first supply period.

[0060] The downtime between the first supply period and the second supply period may be, for example, between 1 minute and 30 minutes.

[0061] In this particle manufacturing method, using the stirring tank 1 of this embodiment makes it possible to efficiently obtain high-quality particles with a high yield.

[0062] The above includes the following disclosures.

[0063] (1) A tank body comprising a bottom and side walls that rise cylindrically from the outer circumference of the bottom, A baffle is provided on the inner side of the aforementioned side wall portion so as to extend vertically, A stirring device that generates a swirling flow in the liquid contained within the tank body, The tank is equipped with a dropping device for dropping additives to be added to the liquid inside the tank, The baffle and the dropping device are arranged in a stirring tank such that the liquid in the tank, which is flowing in a swirling flow, reaches the position where the baffle is provided when it has moved 90 degrees or more but less than 330 degrees from the position where the additive was dropped.

[0064] (2) The agitated tank according to (1), wherein the baffle and the dropping device are arranged such that the liquid in the tank, which is flowing in a swirling flow, reaches the position where the baffle is provided when it has moved 180 degrees or more and 270 degrees or less from the position where the additive was dropped.

[0065] (3) The stirring tank according to (1) or (2), wherein the baffle is arranged such that a gap is formed between it and the side wall portion.

[0066] (4) The stirring tank according to any one of claims (1) to (3), wherein the baffle and the dropping device are arranged such that the dropping position of the additive and the installation position of the baffle lie on the same circumference.

[0067] While further detailed explanations will not be repeated in this specification, the above are merely illustrative examples, and it is possible to appropriately adopt conventionally known technical matters for the stirring tank of the present invention, as long as the effects of the present invention are not significantly impaired. In other words, the present invention is not limited in any way to the above examples. [Examples]

[0068] The present invention will now be described in more detail with reference to examples, but the present invention is not limited to these examples.

[0069] 1. Stirring tank conditions The conditions for the agitated tank are shown in Table 1.

[0070] [Table 1]

[0071] Three types of agitator blades were adopted: the "Twin Star" brand manufactured by Shinko Environmental Solutions Co., Ltd., the oval-shaped three-blade swept-back blade manufactured by Shinko Environmental Solutions Co., Ltd., and the wide paddle blade (product name "Full Zone") manufactured by Shinko Environmental Solutions Co., Ltd. For the "Twin Star" and "Oval-shaped triple-swept wing" designs, a single beavertail baffle was used. Additionally, the "Full Zone Wing" design utilizes two 10% plate baffles. Tap water was used as the liquid in the tank, and the stirring speed under each condition was set to the rotational speed at which the required stirring power per unit volume (Pv value) remained constant.

[0072] 2. Experimental Method 2.1 Two-dimensional PIV measurement A schematic diagram of the experimental apparatus used for PIV measurement is shown in Figure 5. A tank body 10x, made of a transparent acrylic cylinder, and a laser oscillator LBx capable of emitting sheet light SBx were prepared. Sheet light SBx was directed from the side of the tank body 10x towards the rotation axis 32x, and the flow velocity in half of the tank body 10x was measured. The measurements were performed by analyzing images captured by a high-speed camera (CMx) using a computer (PCx). The flow velocity was calculated as the average value from 30,000 samples and used as validation data for the CFD results. For PIV measurement, a two-component PIV system manufactured by Flowtech Research Co., Ltd. was used, and polyamide particles (particle size: 30 μm, density: 1030 kg / m³) were used as tracer particles. 3 ) was used.

[0073] 2.2 Flow analysis For CFD analysis, we used ANSYS's general-purpose thermal fluid analysis code FLUENT19.2, and for modeling and mesh generation, we used Ansys Design Modeler and Ansys Meshing. The turbulence model was the k-ωSST model, and the mixing and dispersion performance was evaluated using the following methods. • First, refer to the flow field. • Calculate the average flow velocity for 10 seconds or more at each location. • Compare the average flow velocity from the PIV measurement results and the CFD analysis results, and validate the CFD analysis results. A 40mm diameter spherical area was colored near the liquid surface of the flow field to act as a tracer, simulating a dropping solution, and the mixing and dispersion processes were observed at each time point. • Compare and evaluate the results of each condition. When using a glass-lined tank for the reaction, the common method of adding the material is by dripping it from a nozzle at the top of the tank. Therefore, the tracer was installed 150 mm from the center of the tank, which corresponds to the nozzle position when scaled down using geometric similarity. The installation orientation of the tracer is shown in Figure 6.

[0074] 3.Results 3.1 Validation of CFD Results Figure 7 shows the PIV and CFD results for vertical flow velocity under each stirring tank condition. The height cross-section of the stirring tank used to evaluate the flow velocity was set in 50mm increments from TL+50mm to 300mm. As a result, we were able to confirm that the flow velocity obtained by CFD was in good agreement with the PIV results.

[0075] 3.2 Mixing and dispersion performance Figure 8 shows the results of the CFD analysis of the mixing and dispersion processes. Regions where the tracer concentration is 0.1 wt% or higher are clearly indicated by coloring.

[0076] 3.2.1 Comparison of Tracer Installation Locations The changes in mixing and dispersion at each input position were compared using a twin-star wing design. The insertion points were set to four positions: 30 degrees upstream from the baffle's position in the circumferential direction, 90 degrees upstream, 180 degrees upstream, and 330 degrees upstream. Figure 9A shows the change in the maximum tracer concentration in the stirred tank, and Figure 9B shows the change in the volume of the region where the tracer concentration is 0.1 wt% or higher.

[0077] Figure 9A shows that immediately after mixing begins, the concentration decreases rapidly at azimuths of 30° and 330°, but gradually reverses at azimuths of 90° and 180°. At azimuths of 30° and 330°, which are close to the baffle, the tracer is introduced into a turbulent flow field, so the tracer is mixed and dispersed immediately after mixing begins. However, the above results are thought to be due to the swirling flow formed at the top of the tank, as shown in Figure 8 from 0.5 to 1.0 seconds, which causes the tracer to move away from the baffle over time, maintaining a high concentration while swirling.

[0078] The tracer concentration when uniformly mixed is approximately 0.06 wt%. Therefore, in the initial stages of mixing, the volume of the region exceeding 0.1 wt% increases as the tracer dispersion progresses, but it decreases once sufficient dispersion has occurred.

[0079] Figure 9B confirms that the fastest dispersion occurs when the tracer is introduced from an orientation of 180°. When introduced from an orientation of 180°, the tracer is drawn towards the center of the tank from just before the baffle while maintaining a high concentration mass, allowing for smooth advection to the bottom of the tank. The tracer, which has been transferred to the bottom of the tank, is further dispersed throughout the tank by the discharge flow from the agitator blades. On the other hand, at azimuths of 30° and 330°, the tracers disperse while swirling in the upper part of the tank before reaching the baffles, resulting in a gradual advection of tracers from the upper to the lower part of the tank. Therefore, it appears that the mixing and dispersion of the entire agitated tank proceeded more quickly at an orientation of 180° compared to orientations of 30° and 330°.

[0080] 3.2.2 Comparison of mixing performance of agitators The mixing and dispersion characteristics of each impeller were compared. The tracer deployment direction was set to the direction furthest from the baffle: Twin Star wing: 180°, Triple Sweep Wing: 180°, Full Zone Wing: 90°. Figure 10A shows the change in the maximum concentration value of the tracer in the stirring tank, and Figure 10B shows the change in the volume of the region where the tracer concentration is 0.1 wt% or higher.

[0081] The results in Figures 8, 10A, and 10B show that when comparing a twin-star wing with an oval-shaped three-swept wing, mixing and dispersion proceed more rapidly in the twin-star wing. As described in Section 3.2.1, in a twin-star wing, the tracer is drawn from in front of the baffle towards the center of the tank, advection to the lower part of the tank progresses, and the tracer is distributed throughout the entire tank. On the other hand, as shown in Figure 8, the oval-shaped triple-swept fin design resulted in slower mixing and dispersion throughout the entire agitated tank because the tracer rotated at the top of the tank and gradually moved to the bottom.

[0082] While twin-star wings and oval-shaped triple-swept wings form a swirling flow at the top of the tank as tracer mixing and dispersion progress, full-zone wings behave in a completely different way. The full-zone blade, with its balanced discharge force between the upper and lower blades, creates an efficient vertical circulation flow and a strong downward flow in the center of the tank. Therefore, immediately after mixing begins, the tracer is transferred to the bottom of the tank, and the strong discharge flow from the wide paddle blades mixes and disperses the tracer. As a result, this method achieved the fastest and most uniform mixing.

[0083] As described above, it was confirmed that good stirring performance is achieved in the azimuth range of 90 degrees to less than 330 degrees for various types of stirring blades. From the above, it can be seen that the present invention improves the diffusion of additives in a stirring tank equipped with baffles. [Explanation of Symbols]

[0084] 1: Stirring tank: 10: Tank body, 12: Bottom, 13: Side wall, 14: Ceiling, 15: Lid, 20:Dripping device, 30: Stirring device, 31: Rotating shaft, 32: Stirring blade, 40: Baffle, 5: Additive tank, 51: Storage tank, 52: Additive supply piping, flow control valve, 100: Particle manufacturing equipment, TF: tank liquid, AF: Additives, SF: swirl flow, CF: Circulating flow.

Claims

1. A tank body comprising a bottom, a side wall portion rising cylindrically from the outer circumference of the bottom, and a ceiling portion positioned opposite the bottom in the vertical direction and closing the upper end of the side wall portion, A baffle is suspended from the ceiling so as to extend vertically with a gap between it and the side wall portion on the inside of the side wall portion, A stirring device that generates a swirling flow in the liquid contained within the tank body, The tank is equipped with a dropping device for dropping additives to be added to the liquid inside the tank, The dropping device is configured to drop the additive onto the surface of the liquid in the tank. The baffle and the dripping device are arranged such that the liquid in the tank, which is flowing in a swirling flow, reaches the position where the baffle is provided when it has moved 120 degrees or more and 270 degrees or less from the position where the additive was dropped. The baffle and the dropping device are arranged in a stirring tank such that the dropping position of the additive and the installation position of the baffle lie on the same circumference.

2. The stirring tank according to claim 1, wherein the stirring device comprises a rotating shaft extending in the vertical direction and rotatable about an axis, and a stirring blade fixed to the rotating shaft, the stirring blade being attached only to the lower end of the rotating shaft.

3. The stirring tank according to claim 1 or 2, wherein there is only one baffle installed.

4. A tank body comprising a bottom, a side wall portion rising cylindrically from the outer circumference of the bottom, and a ceiling portion positioned opposite the bottom in the vertical direction and closing the upper end of the side wall portion, A baffle is suspended from the ceiling so as to extend vertically with a gap between it and the side wall portion on the inside of the side wall portion, A stirring device that generates a swirling flow in the liquid contained within the tank body, A stirring tank is used, which is equipped with a dropping device for dropping additives to be added to the liquid inside the tank. A stirring method comprising stirring the liquid in the tank while dropping the additive onto the surface of the liquid in the tank using the dropping device, thereby diffusing the additive into the liquid in the tank, The dropping position of the additive is set to be on the same circumference as the installation position of the baffle. The dropping of the aforementioned additive is as follows: A stirring method is performed such that the liquid in the tank, which is flowing in a swirling flow, reaches the position where the baffle is provided when it has moved 120 degrees or more and 270 degrees or less from the dropping position.

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