JP2007313484A - Crystallization method and crystallizer - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a crystallization method suppressing the occurrence of secondary cores, and depositing crystal of a large average particle size using a small amount of seed crystal. <P>SOLUTION: In this crystallization method, a solution containing the seed crystal and a compound is supplied to a crystallization tank 200, the solution is agitated with an agitation device 500 provided in the crystallization tank 200, to deposit crystal of the compound on the surfaces of the seed crystal. The agitation device 500 is provided with an agitation means having two flat agitation paddles, and a torque transmitting means receiving torque from a rotary drive means and transmitting it to the agitation means side by reversely rotating two parallel torque outputting shafts to each other. A link mechanism is composed for causing the two agitation paddles to perform figure-of-8 paddle movement in a state of respective angular speeds of the two rotating torque outputting shafts varying complementally. <P>COPYRIGHT: (C)2008,JPO&INPIT

Description

  The present invention relates to a crystallization method and a crystallization apparatus for crystallizing and precipitating a compound dissolved in a solution.

Conventionally, crystallization is performed in which a seed crystal is placed in a solution in which a compound (compound to be taken out as a crystal) is dissolved, and the compound is precipitated in the seed crystal. Crystallization mainly means that crystals are precipitated from the liquid phase, and specific components are separated or concentrated from the liquid phase.
Crystal precipitation includes methods such as cooling crystallization, evaporation crystallization, and reaction crystallization. As an apparatus for obtaining crystals industrially, a DTB type crystallizer and a DP type crystallizer provided with a propeller type agitator in a crystallizer are known (see Fig. 9.18 on page 508 of Non-Patent Document 1). Figure 9.19).
In this crystallization apparatus, a draft tube and a propeller type stirrer are provided in a crystallization tank, and the solution is circulated in a space partitioned by the draft tube by driving of the propeller type stirrer to perform crystallization. Although the crystallizer of Non-Patent Document 1 is described as a continuous evaporation crystallizer, the solution in the tank is circulated by a propeller-type stirrer even in a batch-type crystallizer. What is to be made is known.

However, in the above conventional solution circulation type crystallizer, there is a high rate of occurrence of secondary nucleation (the crystals break down and break up into small crystals, or the broken seed crystals crystallize the compound into small crystals). Therefore, there is a problem that the seed crystal ratio must be increased. The seed crystal ratio is also referred to as a seed crystal addition rate.
There is also a problem that it is difficult to obtain crystals having a relatively large average particle diameter.

Page 508 of Chemical Engineering Handbook (6th revised edition), issued February 25, 1999, editor: Japan Society for Chemical Engineering, publisher: Maruzen Co., Ltd.

  Therefore, an object of the present invention is to provide a crystallization method and a crystallization apparatus capable of suppressing generation of secondary nuclei and depositing a crystal having a large average particle diameter with a small number of seed crystals.

  The present invention provides a crystallization method in which a solution containing a seed crystal and a compound is supplied to a crystallization tank, the solution is stirred by a stirrer provided in the crystallization tank, and a compound crystal is precipitated on the surface of the seed crystal , The stirring means having two flat stirring paddles as the stirring device and the two parallel rotation output shafts rotated in opposite directions in response to the rotational force from the rotation driving means and transmitted to the stirring means side A rotating force transmitting means for connecting the two agitation paddles to each other so that the support shafts penetrating in the thickness direction are arranged in directions orthogonal to each other, The support shafts of the stirring paddles are pivotally connected to the respective tip portions of the two swinging members pivotally connected to the output ends, respectively, and rotated by both the stirring paddles, the swinging members, and the support shafts. The angular velocities of the two rotating output shafts change in a complementary manner. Using a stirrer which constitute a link mechanism for causing the paddle motion-eight to two mixing paddle in a state that provides a crystallization method.

  In the crystallization method, the solution is flowed using a stirring device having two stirring paddles that perform an 8-shaped paddle motion. Since the stirring device can make the flow of the solution in the crystallization tank into a large large vortex, it can suppress the collapse of crystals and seed crystals, and can obtain crystals with a large average particle diameter even with a small number of seed crystals. It becomes possible. In general, it is costly to prepare seed crystals having a uniform particle size, shape, and the like. For this reason, use of a large amount of seed crystals increases the product cost. In this respect, according to the present invention, since a relatively small amount of seed crystal is sufficient, a desired crystal can be obtained at low cost.

The present invention also includes a crystallization tank for containing a seed crystal and a solution containing a compound, and a stirring device provided in the crystallization tank and allowing the solution in the crystallization tank to flow. A stirring means having two shaped stirring paddles, and a rotational force transmitting means for receiving the rotational force from the rotational driving means and rotating two parallel rotational output shafts in opposite directions to transmit them to the stirring means side. Two agitation paddles are integrally connected to each other so that the support shafts penetrating in the thickness direction are arranged in directions orthogonal to each other, and pivoted to the output ends of the rotary output shafts, respectively. The support shafts of the stirring paddles are pivotally connected to the respective tip portions of the two swing members that are connected to each other, and the two rotating outputs during rotation by both the stirring paddles, both the swing members, and both the support shafts. Figure 8 on two stirring paddles with each shaft angular velocity changing in a complementary manner Providing a crystallizer constituting the link mechanism for causing the paddle movement.
In a preferred embodiment of the present invention, there is provided the crystallization apparatus, wherein a draft tube is provided in the crystallization tank, and a stirring device is disposed in the draft tube.

  The crystallizer has a stirrer having two stir paddles that perform an 8-shaped paddle motion. The stirrer can make the solution in the crystallization tank into a slowly large vortex, so that the crystals and seed crystals can be prevented from collapsing, and a crystal having a large average particle diameter can be obtained even with a small number of seed crystals. Become.

  The crystallization method and the crystallization apparatus according to the present invention can suppress the generation of secondary nuclei, and can obtain a crystal having a large average particle diameter with a relatively small amount of seed crystals. Therefore, a crystal having a large particle size can be produced at a low cost.

Hereinafter, the present invention will be specifically described with reference to the drawings.
FIG. 1 shows a schematic diagram of a crystallizer. Reference numeral 100 denotes a crystallization apparatus, 200 denotes a crystallization tank, 300 denotes a draft tube, and 500 denotes a paddle type stirring apparatus. The crystallization apparatus 100 of the present invention can be applied to either a batch type or a continuous type.
The crystallization tank 200 is a tank in which a solution in which a seed crystal and a compound (a target to be crystallized) are dissolved, and has, for example, a body part formed of a substantially cylindrical container.
The crystallization tank 200 is provided with cooling or heating means. The cooling or heating means is not particularly limited. For example, the crystallization tank 200 includes a heat exchanger 101 that circulates a refrigerant or a heat medium around the outer surface of the crystallization tank 200.
In addition, in order to take out the solution containing the grown crystal | crystallization, the discharge path 102 is provided in the bottom face part of the crystallization tank 100. FIG. An introduction path 103 for introducing the solution into the crystallization tank 200 and an introduction path 104 for introducing the seed crystal are provided above the crystallization tank 200.

The draft tube 300 is made of a substantially cylindrical member, and is attached to a substantially central portion of the crystallization tank 200. The solution in the crystallization tank 200 is added until the draft tube 300 is submerged. The draft tube 300 functions as a partition wall that forms a circulating flow for circulating the solution in the crystallization tank 200 in one direction.
The draft tube 300 is made of a material that does not easily deform, for example, metal, hard plastic, or the like.

The diameter D3 of the draft tube 300 is appropriately set according to the size of the crystallization tank 200. The diameter D3 of the draft tube 300 is preferably about 0.5 to 0.8 times the diameter D2 of the body portion of the crystallization tank 200, and more preferably about 0.5 to 0.55 times. If the diameter of the draft tube 300 is too large, the distance between the outer surface of the draft tube 300 and the inner surface of the crystallization tank 200 becomes narrow and the circulation of the solution is poor. On the other hand, if the diameter is too small, the circulation of the solution in the draft tube 300 is performed. Because it gets worse.
Similarly, the height (vertical length) of the draft tube 300 is appropriately set according to the size (liquid level height) of the crystallization tank 200. The height H3 of the draft tube 300 is preferably about 0.3 to 0.7 times the liquid surface height H2 of the solution put in the crystallization tank 200, and further about 0.45 to 0.6 times. More preferred. This is because the solution can be circulated well in the crystallization tank 200.
As a fixing position of the draft tube 300 with respect to the crystallization tank 200, the height h3 from the lower end of the draft tube 300 to the bottom surface of the crystallization tank 200 is 0.2 to 0.4 times the liquid level height H2. The degree is preferable, and about 0.3 to 0.35 times is more preferable. This is because the water flow delivered by the stirring blade is converted as a preferable upward flow between the outer surface of the draft tube 300 and the inner surface of the crystallization tank 200.

In the draft tube 300, a paddle type stirring device 500 is attached.
The stirrer 500 creates a downward circulating flow in which the solution flows from the lower opening of the draft tube 300 to the bottom of the crystallization tank 200, as indicated by the arrows in FIG.
The mounting position of the stirrer 500 is not particularly limited as long as it is between the substantially upper end and the substantially lower end of the tube 300, but is preferably lower than the vertical center of the draft tube 300. This is because the water sent out from the stirring blade can be a strong water flow without being affected by the draft tube 300.

As the paddle type stirring device 500 used in the present invention, for example, the stirring device described in Japanese Patent Application Laid-Open No. 2005-324109 or Japanese Patent No. 3370988 can be used.
Specifically, as shown in FIGS. 2 to 5, the paddle type stirring device 500 includes a device main body 1, a stirring means 2, a rotation driving device 3, and a rotational force transmitting means 4.

The apparatus main body 1 includes an upper base body 11 and a lower base body 12, and upper and lower bearings 13 and 14 are respectively fixed to the apparatus main body 1 at the left and right ends.
A first rotation output shaft 15 is rotatably supported between the left upper and lower bearings 13 and 14, and a first rotation output shaft 15 is provided between the right upper and lower bearings 13 and 14. A parallel second rotation output shaft 16 is rotatably supported.
In addition, a single motor 3 serving as a rotational drive device is disposed at the rear portion of the apparatus main body 1 at a substantially central position, and a drive source transmission shaft 18 is coupled to the rotation shaft 17a of the motor 3. ing.

The agitation means 2 is connected to the first shaft support member 21 fixed to the tip end (output end) of the first rotation output shaft 15 and the tip end (output end) of the second rotation output shaft 16. A fixed second shaft support member 22, a first swing member 24 pivotally supported by a tip end portion of the first shaft support member 21 via a shaft body 23, and a second shaft A stirrer provided between the second swinging member 26 pivotally supported at the tip end portion of the support member 22 via the shaft 25 and the swinging members 24 and 26. 27.
The stirrer 27 has two flat stirring paddles 27A and 27B arranged in directions perpendicular to each other in the thickness direction, and these stirring paddles 27A and 27B are integrated via a connecting portion 27C. ing. Of course, both stirring paddles 27A and 27B may be joined by separate connecting members.

  Each of the first and second swinging members 24 and 26 has a bifurcated portion on the tip side. A first support shaft 28 penetrating the first stirring paddle 27A in the thickness direction is pivotally supported and connected to the bifurcated portions 24a and 24b of the first swing member 24. A second support shaft 29 penetrating the second stirring paddle 27B in the thickness direction is pivotally supported and connected to the bifurcated portions 26a and 26b of the second swing member 26. The first support shaft 28 and the second support shaft 29 are arranged in directions orthogonal to each other.

As shown in FIG. 5, two stirring paddles 27A are twisted by 90 ° by the first and second swinging members 24, 26, the first and second support shafts 28, 29, and the paddle body 27, as shown in FIG. , 27B is moved along an 8-shaped trajectory. The link mechanism 30 causes the two agitation paddles 27A and 27B to perform an 8-shaped paddle motion in a state where the angular velocities of the two rotating output shafts 15 and 16 that are rotating complementarily change.
Output bevel gears 31 and 32 are fixed to the lower ends of the first and second rotary output shafts 15 and 16, respectively.

  The rotational force transmission unit 4 includes a differential gear mechanism having a pair of left and right differential gear output shafts 41 and 42, and the first end of the left differential gear output shaft 41 has the first An original drive gear 43 that meshes with the driven gear 31 on the rotation output shaft 15 side is fixed, while the outer end of the right differential gear output shaft 42 is driven on the second rotation output shaft 16 side. An original bevel gear 44 that meshes with the gear 32 is fixed.

As shown in FIG. 4, the differential gear mechanism includes a reduction bevel gear 45 connected to the drive source transmission shaft 18, a reduction bevel gear 46 meshing with the reduction bevel gear 45, and a large bevel. And a gear box 47 integrally connected to the gear 46.
The reduction bevel gear 46 is rotatably supported on the left differential gear output shaft 41 via a bearing 48, and the gear box 47 is supported on the right differential gear output via a bearing 49. The shaft 42 is rotatably supported.
The gear box 47 includes a left bevel gear 50 fixed to the inner end portion of the left differential gear output shaft 41 and a right portion bevel fixed to the inner end portion of the right differential gear output shaft 42. A first differential bevel gear 54 for fixing, which is fixed to a gear 53, a shaft 53 rotatably supported via a bearing 52, and meshes with the left and right bevel gears 50 and 51, respectively, and a bearing 55. And a second differential bevel gear 57 for intermediary engagement with the left and right bevel gears 50 and 51, respectively.

The paddle type stirring apparatus 500 having the above-described configuration operates as follows.
The rotational force of the motor 3 is transmitted to the differential gear mechanism 4 via the drive source transmission shaft 18. Then, when the reduction small bevel gear 45 in the differential gear mechanism 4 rotates in the arrow direction a in FIG. 4, the reduction large bevel gear 46 rotates in the arrow b direction integrally with the gear box 47. The rotation of the gear box 47 also causes the first and second intermediate differential bevel gears 54 and 57 to rotate together, so that the left and the second intermediate differential bevel gears 54 and 57 mesh with each other. The right and left bevel gears 50 and 51 and the left and right differential gear output shafts 41 and 42 also rotate together in the direction of the arrow b, and the left and right original moving gears 43 and 44 rotate.

  The rotation output shaft 15 on the left side is driven to rotate in the direction of the arrow c through the driven gear 31 by the rotation of the left driving gear 43, while the driven gear 32 is rotated by the rotation of the right driving gear 44. Accordingly, the rotation output force shaft 16 on the right side is rotationally driven in the direction of the arrow d opposite to the rotation output shaft 15.

Since the rotation of the first and second rotation output shafts 15 and 16 is transmitted to the link mechanism 30 via the shaft support members 21 and 22, the two agitation paddles 27A and 27B are formed in an 8-character shape. Paddle exercise is performed while drawing the trajectory. Details of the movement of the figure 8 locus are disclosed in Japanese Patent No. 3370988, and the description thereof will be omitted.
A specific example of such a paddle type agitator is “Vortex Generator Octagit” (trade name) manufactured by Nomura Micro Science Co., Ltd.

Next, the crystallization method of the present invention will be described.
A solution in which a compound to be precipitated is dissolved is placed in a crystallization tank, and seed crystals are charged therein. The solution is preferably a saturated solution (predetermined temperature) of the compound. Preferably, the saturated solution at a predetermined temperature is heated by a heating means to completely dissolve the undissolved compound.
Next, the stirring device is activated. Due to the operation of the stirring device, the flow of the solution flows from the inside of the draft tube to the lower opening of the draft tube, flows outward at the bottom of the crystallization tank, and from between the body of the crystallization tank and the outside of the draft tube. It rises and becomes a circulating flow that flows to the upper opening of the draft tube (arrow shown in FIG. 1). The flow of the solution in the crystallization tank formed by the paddle type stirring device becomes a slow and large vortex and can suppress the collapse of crystals and seed crystals.
Then, by circulating the solution in the crystallization tank and cooling the solution by the cooling means, the supersaturated compound is crystallized on the surface of the seed crystal.

  The rotation speed of the paddle type stirring device is appropriately set according to the amount of the solution and the like. For example, 150 to 200 rpm is preferable when the amount of the solution is 100 liters, and 70 to 100 rpm is preferable when the amount of the solution is 400 liters.

The stirring time by the paddle type stirring device is appropriately set according to the amount of the solution, the type of the target compound, the amount of seed crystals, and the like. The cooling rate is also appropriately set according to the solubility curve of the target compound. For example, when potassium alum (KAl (SO ₄ ) ₂ · 18H ₂ O) is precipitated as a compound, cooling from 50 ° C. to 20 ° C. is exemplified for 3 hours.

The ratio of the seed crystal is not particularly limited, but is generally designed appropriately in consideration of an ideal growth curve.
For the ideal growth curve, see “Recent Progress in Chemical Engineering Crystallization Optics and Crystallization Process” (issued October 30, 2001, edited by the Kanto Branch of the Chemical Society of Japan, Publisher: Chemical Society of Japan) ) Pages 5-6.
In the present invention, a crystal having a relatively large particle size can be obtained even if the ratio of seed crystals is reduced. Here, the seed crystal ratio is obtained by seed crystal input amount [kg] / ideal crystallization amount [kg].
In the present invention, when the surface area of the crystal is the same, good results can be obtained even when the amount of seed crystal to be added is 1/4 to 1/2 times that of the method of crystallization with a propeller type stirring device. .
The size and shape of the seed crystal are not particularly limited, and are appropriately set according to the size and shape of the crystal to be obtained.

  Hereinafter, the present invention will be described in more detail with reference to Examples and Comparative Examples. However, the present invention is not limited to the following examples.

Example 1
A bottomed cylindrical tank made of stainless steel with a diameter of 40 cm and a height of 65 cm, a plastic cylindrical draft tube with a diameter of 25 cm and a height of 35 cm, and two stirring paddles (the length of both ends of the paddle is 13 cm) A paddle type stirring device (manufactured by Nomura Micro Science Co., Ltd., trade name: Octagit, model: OT-10S type) arranged in an orthogonal direction was prepared. As shown in FIG. 6A, the draft tube B was fixed in the tank A so as to have a distance of 7.5 cm from the inner surface A1 of the trunk portion of the tank A and 20 cm from the bottom surface A2 of the tank A. The stirring device C was fixed in the draft tube B so that the lower end C1 of the paddle was 15 cm from the lower end B1 of the draft tube B. The paddle type stirring device C was installed so as to flow the solution from the upper side to the lower side.
In this tank, 80 liters of 35 ° C. saturated solution of potassium alum is added and seeds of potassium alum (average grain size of seed crystal: 75 μm, seed crystal ratio: 0.007) are added up to 50 ° C. After raising the temperature, crystallization was performed by gradually cooling to 20 ° C. over 3 hours while rotating the paddle type stirring device (rotation speed: 180 rpm).

(Example 2)
Crystallization was performed in the same manner as in Example 1 except that seed crystals having an average particle diameter of 125 μm were used and the seed crystal ratio was 0.024.

(Example 3)
Crystallization was performed in the same manner as in Example 1 except that seed crystals having an average particle diameter of 150 μm were used and the seed crystal ratio was set to 0.035.

(Comparative Example 1-1)
A tank in which a baffle plate with a width of 5 cm and a height of 40 cm is fixed at equal intervals in the circumferential direction on a barrel portion of a cylindrical tank with a diameter of 40 cm and a height of 65 cm, and three propellers rotate one Propeller type stirring device (manufactured by ASONE Co., Ltd., trade name: portable stirrer, model number: P82-V90S-11) fixed in a state tilted in the same direction on the shaft Prepared. As shown in FIG. 6B, the propeller type stirring device C is placed at the center of the tank A with the baffle plate D so that the lower end C1 of the propeller is at a distance of 20 cm from the bottom surface A2 of the tank A. Fixed. The propeller type stirring device was installed so that the solution could flow from the upper side to the lower side.
In this tank, 80 liters of 35 ° C. saturated solution of potassium alum is added and seeds of potassium alum (average grain size of seed crystal: 75 μm, seed crystal ratio: 0.007) are added up to 50 ° C. After the temperature was raised, crystallization was performed by gradually cooling to 20 ° C. over 3 hours while rotating the propeller type stirring device (rotational speed: 420 rpm).

(Comparative Example 1-2)
Crystallization was performed in the same manner as Comparative Example 1-1 except that seed crystals having an average particle diameter of 125 μm were used and the seed crystal ratio was 0.024.

(Comparative Example 1-3)
Crystallization was performed in the same manner as in Comparative Example 1-1 except that seed crystals having an average particle diameter of 150 μm were used and the seed crystal ratio was 0.035.

(Comparative Example 2-1)
A bottomed cylindrical tank having a diameter of 40 cm and a height of 65 cm, a cylindrical draft tube having a diameter of 25 cm and a height of 35 cm, and the same propeller-type stirring device as Comparative Example 1-1 were prepared. As shown in FIG. 6 (c), the draft tube B was fixed in the tank A so as to have a distance of 7.5 cm from the body inner surface A 1 of the tank A and 20 cm from the bottom surface A 2 of the tank A. The stirring device C was fixed in the draft tube B so that the lower end C1 of the propeller was 20 cm from the lower end B1 of the draft tube B. The propeller type stirring device was installed so that the solution could flow from the upper side to the lower side.
In this tank, 80 liters of 35 ° C. saturated solution of potassium alum is added and seeds of potassium alum (average grain size of seed crystal: 75 μm, seed crystal ratio: 0.007) are added up to 50 ° C. After raising the temperature, crystallization was carried out by gradually cooling to 20 ° C. over 3 hours while rotating the propeller type stirring device (rotational speed: 300 rpm).

(Comparative Example 2-2)
Crystallization was performed in the same manner as Comparative Example 2-1, except that seed crystals having an average particle diameter of 125 μm were used and the seed crystal ratio was 0.024.

(Comparative Example 2-3)
Crystallization was performed in the same manner as in Comparative Example 2-1, except that a seed crystal having an average particle diameter of 150 μm was used and the seed crystal ratio was 0.035.

<Result>
The evaluation of the crystals obtained in the above Examples and Comparative Examples is shown in FIG. In FIG. 7, the vertical axis represents the ideal growth ratio and the growth ratio of the obtained crystal, and the horizontal axis represents the seed crystal ratio.
When Example 1 having a seed crystal grain size of 75 μm and a seed crystal ratio of 0.007 is compared with Comparative Examples 1-1 and 2-1 corresponding thereto, Example 1 is more ideal. It was confirmed that good crystals were obtained near the growth ratio.
Even if Example 2 in which the seed crystal grain size is 125 μm and the seed crystal ratio is 0.024 is compared with Comparative Example 1-2 and Comparative Example 2-2 corresponding thereto, the same is true. Even when Example 3 having a crystal grain size of 150 μm and a seed crystal ratio of 0.035 was compared with Comparative Examples 1-3 and 2-3 corresponding thereto, excellent crystals were similarly obtained. It was confirmed that it was obtained.

The ideal growth ratio, the growth ratio of the obtained crystal, and the seed crystal ratio can be obtained by the following equations, respectively.
-Ideal growth ratio = Lsp / Ls
-Crystal growth ratio = Lwp / Ls
-Seed crystal ratio = Ws / Wth
However, “Lsp” is an ideal crystal grain size [m], “Ls” is a seed crystal average grain size [m], and “Lwp” is an average grain size [m] of the obtained crystal, “Ws” represents the seed crystal input [kg], and “Wth” represents the ideal crystallization amount [kg].
Further, the above formula can be derived from the following formula.
Ls = {Ws / (p × Kv × Ns)} ^1/3
Lsp = {(Ws + Wth) / (p × Kv × Ns)} ^1/3
Lsp / Ls = {(1 + Cs) / Cs} ^1/3
Wth = (35 ° C. solubility of potassium alum -20 ° C. solubility) × solvent amount [kg]
Lwp = {(Ws + Wp) / (p × Kv × Np)} ^1/3
However, “Ws” is the seed crystal input [kg], “Wth” is the ideal crystallization amount [kg], “p” is the crystal density [kg / m ³ ], and “kv” is , “Ns” represents the number of crystals, and “Cs” represents the seed crystal ratio.

Next, FIG. 8 shows the particle size distribution of the crystals obtained in Example 1, Comparative Example 1-1, and Comparative Example 2-1, and FIG. 9 shows Example 2, Comparative Example 1-2, and Comparative Example 2. FIG. 10 shows the particle size distribution of the crystals obtained in Example-2, Comparative Example 1-3, and Comparative Example 2-3.
As shown in each figure, it can be seen that in Examples 1 to 3, crystals having a large crystal grain size were obtained.

Schematic which shows one Embodiment of a crystallization apparatus. Front sectional drawing which shows a paddle type stirring apparatus. The right side sectional view showing the agitator. Sectional drawing which shows a rotation transmission means. Reference drawing explaining the link mechanism. (A) is the schematic of the apparatus used in Examples 1-3, (b) is the schematic of the apparatus used in Comparative Examples 1-1 to 1-3, (c) is Comparative Example 2-1. Schematic of the device used in ~ 2-3. The graph which shows the growth ratio of the crystal | crystallization obtained by each Example and each comparative example. The graph which shows the particle size distribution of the crystal | crystallization obtained by the Example and each comparative example. The graph figure same as the above. The graph figure same as the above.

Explanation of symbols

DESCRIPTION OF SYMBOLS 100 ... Crystallizer, 200 ... Crystallization tank, 300 ... Draft tube, 500 ... Paddle type stirring apparatus

Claims (3)

In a crystallization method in which a solution containing a seed crystal and a compound is supplied to a crystallization tank, the solution is stirred by a stirrer provided in the crystallization tank, and a crystal of the compound is precipitated on the surface of the seed crystal.
As the stirring device, the stirring means having two flat stirring paddles and the rotational force from the rotation driving means are rotated to rotate the two parallel rotation output shafts in opposite directions to transmit to the stirring means side. A rotational force transmission means, and integrally connected to each other so that the respective support shafts penetrating the two stirring paddles in the respective thickness directions are arranged in directions orthogonal to each other; The respective support shafts of the stirring paddles are pivotally connected to the respective tip portions of the two swinging members pivotally connected to the output ends, respectively, and two stirring paddles, both swinging members and both support shafts are used to A crystallization method characterized by using a stirrer having a link mechanism for causing a stirring paddle to perform a paddle motion of an eight-shape. A crystallization tank in which a solution containing a seed crystal and a compound is placed, and a stirring device provided in the crystallization tank and flowing the solution in the crystallization tank,
The agitator receives the rotational force from the agitating means having two flat agitating paddles and the rotational driving means, and rotates two parallel rotation output shafts in opposite directions to transmit to the agitating means side. A rotational force transmission means, and integrally connected to each other so that the respective support shafts penetrating the two stirring paddles in the respective thickness directions are arranged in directions orthogonal to each other; The respective support shafts of the stirring paddles are pivotally connected to the respective tip portions of the two swinging members pivotally connected to the output ends, respectively, and two stirring paddles, both swinging members and both support shafts are used to A crystallizer characterized in that it comprises a link mechanism that causes a stirring paddle to perform a paddle motion of an eight-shape. The crystallization apparatus according to claim 2, wherein a draft tube is provided in the crystallization tank, and the stirring device is disposed in the draft tube.