JP6870301B2 - Crystallization reaction tank and crystallization classification device using this - Google Patents

Description

The present invention relates to a crystallization reaction tank and a crystallization classification device using the same. In particular, in a continuous stirring tank, particles having a desired particle size or larger are simultaneously discharged while efficiently performing a crystallization reaction in the tank. The present invention relates to a crystallization reaction tank and a crystallization classification device using the crystallization reaction tank.

Conventionally, in a crystallization reaction tank, the supplied raw materials react and the nuclei generated in the supersaturated region or the seed crystal particles supplied separately from the raw materials are uniformly dispersed in the tank to efficiently produce the raw materials. It is undergoing a crystallization reaction.

Further, in the case of a continuous crystallization reaction tank, there are many cases where the crystallization reaction is carried out in the tank and overflow or continuously discharged from the bottom of the tank (see, for example, Patent Document 1 and Non-Patent Document 1).

Japanese Unexamined Patent Publication No. 2012-120629

SCEJ80th Annual meeting, Lecture No. E114, Role of stirring and mixing in crystallization operation, Tsukishima Kikai

However, when the reaction tank is a single tank, the time for each crystallization particle to stay in the tank is different, so that the crystallization reaction varies and a particle size distribution occurs. Therefore, when it is desired to extract particles having a desired particle size or larger to obtain a product, a classification operation of the crystallization particles is required as a post-process of crystallization by this crystallization reaction tank, and the installation cost of the classification equipment and its running are required. There was a problem that extra costs were required.

Therefore, in the present invention, by providing a draft tube which is a cylindrical housing in a continuous stirring tank and providing a plurality of types of stirring blades, a desired particle size can be obtained while efficiently performing a crystallization reaction in one stirring tank. It is an object of the present invention to provide a crystallization reaction tank having a classification function capable of extracting the above particles and a crystallization classification device using the crystallization reaction tank.

In order to achieve the above object, the crystallization reaction tank according to one aspect of the present invention includes a stirring tank for holding a crystallization raw material and a stirring tank.
A rotating shaft extending in the vertical direction in the stirring tank,
A draft tube provided so as to surround a predetermined depth region around the rotation axis, and
A first stirring blade fixed to the rotating shaft and provided in the draft tube,
It has a second stirring blade fixed to the rotating shaft and provided outside the draft tube.
The first stirring blade is provided in the draft tube so as to form an upward flow of the crystallization raw material.
The second stirring blade is provided above the draft tube so as to form a downward flow of the crystallization raw material outside the draft tube, and is supported by a support portion radially extending from the rotation axis. And provided only on the outside of the draft tube in the radial direction.

According to the present invention, a stable circulating flow can be formed in the tank, and a stable low-speed ascending flow can be formed in the center of the bottom of the tank. By forming such an in-tank flow, efficiency in the tank can be formed. While generating a crystallization reaction, particles having a desired particle size or larger can be efficiently deposited and discharged at the bottom of the tank.

It is a figure which showed an example of the crystallization reaction tank which concerns on embodiment of this invention, and the crystallization classification apparatus which includes this. It is an enlarged view which extracted and showed the main part of the crystallization reaction tank which concerns on embodiment of this invention. It is a figure which showed the parameter setting and the simulation result of the crystallization reaction tank which concerns on embodiment of this invention. FIG. 3A is a diagram showing an example of parameter setting of the crystallization reaction tank according to the embodiment of the present invention. FIG. 3B is a diagram showing a simulation result of the flow of the crystallization raw material in the crystallization reaction tank according to the present embodiment. It is a figure which showed the parameter setting and the simulation result of the crystallization reaction tank which concerns on Comparative Example 1. FIG. 4A is a diagram showing an example of parameter setting of the crystallization reaction tank according to Comparative Example 1. FIG. 4B is a diagram showing a simulation result of the flow of the crystallization raw material in the crystallization reaction tank according to Comparative Example 1. It is a figure which showed the parameter setting and the simulation result of the crystallization reaction tank which concerns on Comparative Example 2. FIG. 5A is a diagram showing an example of parameter setting of the crystallization reaction tank according to Comparative Example 2. FIG. 5B is a diagram showing a simulation result of the flow of the crystallization raw material in the crystallization reaction tank according to Comparative Example 2. It is a figure which showed the concentration distribution of the solid particle of the crystallization reaction tank which concerns on Comparative Examples 3 and 4. FIG. 6A is a diagram showing the concentration distribution of solid particles in the entire crystallization reaction tank according to Comparative Example 3. FIG. 6 (b) is an enlarged view of the bottom of FIG. 6 (a). FIG. 6C is a diagram showing the concentration distribution of solid particles in the entire crystallization reaction tank according to Comparative Example 4. FIG. 6 (d) is an enlarged view of the bottom of FIG. 6 (c).

Hereinafter, embodiments for carrying out the present invention will be described with reference to the drawings.

FIG. 1 is a diagram showing an example of a crystallization reaction tank and a crystallization classification device including the crystallization reaction tank according to the embodiment of the present invention. The crystallization reaction tank 50 according to the embodiment of the present invention includes a stirring tank 10, a stirrer 20, a draft tube 30, a draft tube fixing jig 35, and a baffle plate 40. The crystallization classification device 100 further includes a crystallization raw material supply device 60 and a classification outlet 70 in addition to the crystallization reaction tank 50.

The stirring tank 10 is a means for holding the crystallization raw material 110 in the tank, and is a means for stirring the crystallization raw material 110 held in the tank to generate and accelerate the crystallization reaction. The crystallization raw material 110 is in a liquid state or a slurry state composed of liquid and fine particles when the raw material is charged, but as the crystallization reaction progresses, solid particles 111 are generated and the particle size of the solid particles 111 increases. I will go. Therefore, the stirring tank 10 usually holds the crystallization raw material 110 in which the liquid and the solid particles 111 are mixed in the tank.

The stirring tank 10 is preferably formed in a cylindrical shape having a mirror bottom. Having the above shape facilitates the formation of a circulating flow that circulates up and down. A specific description of the circulating flow will be described later.

As the crystallization raw material 110, various raw materials may be selected depending on the crystallization target and the application. For example, the crystallization raw material 110 for crystallizing the solid Ni particles 111 may be used.

The stirrer 20 is a stirring means for stirring the crystallization raw material 110 in the stirring tank 10. The stirrer 20 includes a rotary shaft 21, a main stirring blade support portion 22, a main stirring blade 23, an auxiliary stirring blade support portion 24, an auxiliary stirring blade 25, and a motor 26. The rotary shaft 21 may be provided at an arbitrary position in the stirring tank 10, but is generally provided near the center of the stirring tank 10 by rotating the main stirring blade 23 and the auxiliary stirring blade 25. It is installed so that a symmetrical flow can be generated in the stirring tank 10 around the rotating shaft 21. The rotating shaft 21 is provided so as to extend in the vertical direction, and rotates the main stirring blade 23 and the auxiliary stirring blade 25 horizontally.

The main stirring blade support portion 22 is a supporting means for supporting the main stirring blade 23. The main stirring blade support portion 22 is fixedly provided on the rotating shaft 21 and plays a role of transmitting the rotation of the rotating shaft 21 to the main stirring blade 23.

The main stirring blade 23 may be configured to have various shapes depending on the application. For example, the main stirring blade 23 may be formed in the horizontal direction or the vertical direction in order to form a vertical flow of the crystallization raw material 110 in the draft tube 30. On the other hand, it may be provided with an inclination. By being provided with an inclination, it is possible to form a vertical flow that pushes out the crystallization raw material 110 vertically. The details of the configuration of the stirring blade 23 will be described later.

The main stirring blade 23 preferably has a shape extending in the horizontal direction (left-right direction) with the rotation shaft 21 as the center. As a result, the rotation of the rotating shaft 21 can be efficiently transmitted to the crystallization raw material 110 without loss, and a flow symmetrical with respect to the rotating shaft 21 can be formed.

One or more main stirring blades 23 are provided around the main stirring blade support portion 22. When each of the main stirring blades 23 extending to the left and right with the rotation shaft 21 as the center is counted as one, at least one main stirring blade 23 may be provided, and a plurality of main stirring blades 23 may be provided depending on the application. In the present embodiment, two main stirring blades 23 will be provided in each of the upper and lower stages.

The main stirring blade support portion 22 and the main stirring blade 23 may be provided in a plurality of stages in the vertical direction. In FIG. 1, one unit of the stirring blade support portion 22 and one unit of the stirring blade 23 are provided in the upper stage and the lower stage. If the length of the stirring tank 10 becomes long, it becomes difficult to create a sufficient flow of the crystallization raw material 110 with only one stage. Therefore, when the stirring tank 10 is vertically long, the main stirring blade support portion 22 and The main stirring blade 23 is often provided with one unit each in the upper stage and the lower stage. Also in this embodiment, an example in which the main stirring blade support portion 22 and the main stirring blade 23 are provided one unit each in the upper stage and the lower stage will be described.

The main stirring blade 23 is configured to form an ascending flow of the vertical flow. In the present embodiment, in addition to the main stirring blade 23 being provided inside the draft tube 30, the auxiliary stirring blade 25 is provided above the draft tube 30, and the auxiliary stirring blade 25 crystallizes downward. It plays a role in forming the flow of the raw material 110. Therefore, in order to form a vertical circulation flow inside and outside the draft tube 30, the main stirring blade 23 functions to form an ascending flow of the crystallization raw material 110 in the draft tube 30.

The auxiliary stirring blade 25 is a stirring blade provided for forming a downward flow and rectifying it on the outside of the draft tube 30, that is, between the outer peripheral surface of the draft tube 30 and the inner peripheral surface of the stirring tank 10. Since the main stirring blade 23 can independently form a circulating flow in the vertical direction inside and outside the draft tube 30, the circulating flow itself can be formed even if the auxiliary stirring blade 25 is not provided. it can. However, since the main stirring blade 23 is provided inside the draft tube 30, the influence of the draft tube 30 on the downward flow is naturally weakened. Therefore, in the crystal precipitation reaction tank 50 according to the present embodiment, the downward flow from the upper part to the lower part of the stirring tank 10 is strengthened by installing the auxiliary stirring blade 25 on the upper outside of the draft tube 30 and stirring the mixture. However, the circulating flow formed in the entire stirring tank 10 is strengthened to increase the rectifying effect. As a result, a good circulating flow can be formed in the entire inside of the stirring tank 10, and the crystallization reaction can be promoted.

From this point of view, the auxiliary stirring blade 25 is provided on the outside of the draft tube 30 in both the height direction and the radial direction, and acts only on the downward flow of the crystallization raw material 110 on the outside of the draft tube 30, and is a draft tube. The arrangement does not affect the ascending current inside the 30.

The auxiliary stirring blade support portion 24 is a member for supporting the auxiliary stirring blade 25, is fixed to the rotating shaft 21 and extends radially from the rotating shaft 21 along the radial direction, and the outer auxiliary stirring blade 25 is inside. Support from. The auxiliary stirring blade support portion 24 is composed of rod-shaped members such as a cylinder and a prism that do not have a paddle-like shape, and is configured so as not to affect the ascending flow in the draft tube 30.

As described above, the crystallization reaction tank 50 and the crystallization classification device 100 according to the present embodiment are provided with the main stirring blade 23 inside the draft tube 30 and the auxiliary stirring blade 25 outside the draft tube 30. A good crystallization raw material 110 can form a circulating flow in the vertical direction.

The motor 26 is a driving means for rotating the main stirring blade 23 and the auxiliary stirring blade 25 via the main stirring blade support portion 22 and the auxiliary stirring blade support portion 24, and causes the main stirring blade 23 and the auxiliary stirring blade 25 to rotate. Various motors 26 may be used as long as they can be rotated at an appropriate speed and torque.

The draft tube 30 is provided to regulate the flow in the stirring tank 10 and functions as a rectifying member. The draft tube 30 has a cylindrical shape and is provided so as to surround a predetermined depth region around the rotating shaft 21 and the main stirring blade 23. The draft tube 30 causes the vertical flow of the crystallization raw material 110 formed by the main stirring blade 23 to follow the inner peripheral surface thereof, and forms an upward unidirectional flow, that is, an ascending flow in the draft tube 30. Play a role.

In order to appropriately form such an ascending flow of the crystallization raw material 110, it is preferable to appropriately set the diameter (inner diameter) of the draft tube 30 which is a rectifying member with respect to the horizontal diameter of the stirring blade 23. .. That is, the circulation flow inside and outside the draft tube 30 can be formed even in the cooperation between the main stirring blade 23 and the auxiliary stirring blade 25, but a better circulation flow can be formed by appropriately setting the draft tube 30. Can be formed. In the present embodiment, an appropriate setting method of such a draft tube 30 will also be described, but the detailed contents thereof will be described later.

The draft tube 30 can be made of various materials, and may be made of, for example, stainless steel.

The draft tube fixing jig 35 is a jig for fixing the draft tube 30. In FIG. 1, a configuration is shown in which the draft tube fixing jig 35 is fixed to the baffle plate 40, and the draft tube fixing jig 35 further fixes the inner draft tube 30, but the draft tube fixing jig The 35 may have various configurations as long as the draft tube 30 can be fixed in an appropriate position.

The obstruction plate 40 is a rectifying plate for converting the lateral and diagonal flows of the crystallization raw material 110 into the vertical direction or the axial flow direction, and extends in the vertical direction along the inner peripheral side surface of the stirring tank 1. At the same time, it is provided so as to project toward the center of the stirring tank 10, that is, the rotating shaft 21. Specifically, the baffle plate 40 plays a role of forming a vertical flow of the crystallization raw material 110 between the outer peripheral side surface of the draft tube 30 and the inner peripheral side surface of the stirring tank 10. As described above, when a vertical flow is formed inside the draft tube 30, the vertical flow inside the draft tube 30 is formed between the draft tube 30 and the stirring tank 10. Form a vertical flow in the opposite direction to. As a result, the crystallization raw material 110 can form a circulating flow that circulates up and down inside and outside the draft tube 30, promotes the crystallization reaction, and efficiently produces the crystallized solid particles 111 according to the particle size. Can be sorted up and down. That is, the solid particles 111 that have not reached the predetermined particle size can be raised by the ascending flow, and the solid particles 111 that have reached the predetermined particle size are quickly deposited on the bottom of the stirring tank 10. Can be done.

The baffle plate 40 is provided so as to sandwich the draft tube 30 from both sides, that is, to form a pair. For example, the baffle plates 40 may be provided in pairs so as to sandwich the draft tubes 30 from the left and right, or may be provided in pairs so as to sandwich the draft tubes 30 from four directions. Alternatively, more may be provided as needed. In this way, the number of baffle plates 40 may be appropriately determined according to the intended use. The baffle plate 40 may be called a baffle 40.

The above are the components of the crystallization reaction tank 50 according to the embodiment of the present invention. The crystallization classification device 100 according to the embodiment of the present invention further includes a crystallization raw material input device 60 and a classification outlet 70. ..

The crystallization raw material input device 70 is a means for charging the crystallization raw material 110 into the stirring tank 10, and includes a crystallization raw material tank 61 and a crystallization raw material input port 62. The crystallization raw material tank 61 is a tank for accumulating the crystallization raw material 110, and for example, the slurry-like crystallization raw material 110 is stored. The crystallization raw material input port 62 is a raw material input port or a raw material supply port for charging or supplying the crystallization raw material 110 accumulated in the crystallization raw material tank 61 into the stirring tank 10.

The classification outlet 70 is a product outlet for discharging fixed particles having a predetermined particle size or larger from the stirring tank 10, and is provided by being connected to the bottom of the stirring tank 10. Thereby, solid particles 111 having a desired particle size classified can be obtained.

FIG. 2 is an enlarged view showing an extracted main part of the crystallization reaction tank 50 according to the embodiment of the present invention. As shown in FIG. 2, a draft tube 30 is provided around the main stirring blade 23 of the stirrer 20, and an auxiliary stirring blade 25 is provided above the draft tube 30. Further, a baffle plate 40 is provided on the inner peripheral side surface of the stirring tank 10 outside the draft tube 30.

Here, the stirrer 20 includes a main stirring blade 23 in which a rotating shaft 21 is provided at the axis of the stirring tank 10 and is rotatable in the draft tube 30, and an auxiliary stirring blade 25 that is rotatable above and outside the draft tube 30. Has. The main stirring blade 23 and the auxiliary stirring blade 25 have shapes such as an inclined paddle and an inclined turbine having a function of generating an axial flow. The shapes and dimensions of the main stirring blade 23 and the auxiliary stirring blade 25 can be determined by simulation by setting the flow velocities inside and outside the draft tube based on the true specific gravity of the particles and the end speed of the particle diameter to be classified. Both the upper and lower stages of the main stirring blade 23 are configured as an inclined stirring paddle, and extend horizontally outward from the main stirring blade support member 22 and intersect each other at right angles to form a cross. Two are provided. Further, in the auxiliary stirring blade 25, above the draft tube 30, the auxiliary stirring blade support portion 24 extends radially horizontally from the rotation shaft 21 to the outside of the draft tube 30 so as to form a cross, and the auxiliary stirring blade 25 extends to the outside of the draft tube 30. Wings 25 are provided. In FIG. 2, two pairs of auxiliary stirring blades 25 are provided in a cross shape, but the number and shape of the auxiliary stirring blades 25 can be variously configured depending on the application.

Further, the draft tube 30 is provided so as to be supported upright on the axial center portion in the stirring tank 10. The draft tube 30 has a cylindrical shape and is provided so as to cover the stirring blade 23 at a predetermined distance from the tip of the stirring blade 23. By installing the draft tube 30, the rectifying effect in the stirring tank 10, the reduction of the stirring machine power by the rectification, and the slurry separation effect are expected.

A pair or more of the baffle plates 40 are installed radially so as to project toward the axis of the stirring tank 10. FIG. 2 shows an example in which two pairs of baffle plates 40 are installed so as to form a cross from four directions.

As described above, the crystallization reaction tank 50 according to the embodiment of the present invention has a configuration in which the draft tube 30 is provided around the stirring blade 23.

Next, the result of determining the ratio of the diameter of the draft tube to the total length of the stirring blade 23 such that the crystallization raw material 110 forms a vertical flow in the draft tube 30 will be described by a simulation experiment. The simulation experiment is performed on the case where the agitator 20 is provided with only the main agitating blade 23 without the auxiliary agitating blade 25, but the correlation with the draft tube 30 is overwhelming with the main agitating blade 23. Since the auxiliary stirring blade 25 is configured to affect only the downward flow outside the draft tube 30, the simulation experiment is almost as it is in the crystallization reaction tank 50 and the crystallization classification according to the present embodiment. It is applicable to the device 100.

In the simulation experiment, the diameter of the stirring tank 10 was φ430 mm, the diameter of the main stirring blade 23 was φ170 mm, the paddle width was 25 mm, and four pitched paddles were used. Under the conditions where the height of the liquid level from the bottom surface of the tank 10 is set to 445 mm and the rotation speed of the main stirring blade 23 is set to 600 rpm, the continuous phase is a liquid and the dispersed phase is a solid particle of 50 μm. I went as 43.

FIG. 3 is a diagram showing parameter settings and simulation results of the crystallization reaction tank 50 according to the embodiment of the present invention. FIG. 3A is a diagram showing an example of parameter setting of the crystallization reaction tank 50 according to the embodiment of the present invention. As shown in FIG. 3A, in an example of the crystallization reaction tank 50 according to the present embodiment, when the total length of the main stirring blade 23 is d and the diameter of the draft tube 30 is D, D / d. Set to = 1.4.

FIG. 3B shows the crystallization raw material 110 in the crystallization reaction tank 50 according to the embodiment when the ratio D / d of the diameter D of the draft tube 30 to the total length d of the main stirring blade 23 is 1.4. It is the figure which showed the simulation result of the flow.

As shown in FIG. 3B, almost all of the flow of the crystallization raw material 110 in the draft tube 30 is an upward flow, and an upward axial flow is formed. Further, almost all of the flow flows downward between the draft tube 30 outside the draft tube 30 and the inner peripheral side surface of the stirring tank 10, and a circulating flow circulating inside and outside the side surface of the draft tube 30 is formed. Has been done. By appropriately setting the ratio between the diameter D of the draft tube 30 and the total length d of the main stirring blade 23, the draft tube 30 flows in one direction in the vertical direction and flows outside the draft tube 30. Can form a circulating flow flowing in the other direction in the vertical direction opposite to the inside of the draft tube 30, and the crystallization raw material 110 can be efficiently circulated in the axial flow direction.

Note that D / d = 1.4 is an example, and the ratio D / d of the diameter D of the draft tube to the total length d of the main stirring blade 23 varies as long as a circulating flow can be formed inside and outside the draft tube 30. Can be set to the value of.

As described above, in the crystallization reaction tank 50 and the crystallization classification device 100 according to the present embodiment, the draft tube 30 is installed in the stirring tank 10, a stable circulating flow is formed in the tank, and the center of the bottom of the tank is formed. It has a classification function of forming a stable ascending flow at a low velocity and efficiently depositing particles having a desired particle size or larger in that region.

Next, the parameter setting of the crystallization reaction tank according to the comparative example will be described.

FIG. 4 is a diagram showing parameter settings and simulation results of the crystallization reaction tank according to Comparative Example 1. FIG. 4A is a diagram showing an example of parameter setting of the crystallization reaction tank according to Comparative Example 1. As shown in FIG. 4A, in the crystallization reaction tank according to Comparative Example 1, when the total length of the main stirring blade 123 is d and the diameter of the draft tube 130 is D, D / d = 1. Set to 1. In this case, the distance between the tip of the main stirring blade 123 and the inner peripheral surface of the draft tube 130 is the draft and the tip of the stirring tank 23 of the crystallization reaction tank 50 according to the embodiment shown in FIG. 3 (a). It is narrower than the distance from the tube 30.

FIG. 4B shows the crystallization raw material 110 in the crystallization reaction tank according to Comparative Example 1 when the ratio D / d of the diameter D of the draft tube 130 to the total length d of the main stirring blade 123 is 1.1. It is the figure which showed the simulation result of the flow.

As shown in FIG. 4B, the ascending flow on the left side formed by the main stirring blade 123 collides with the inner peripheral surface of the draft tube 130 on the way, and a meandering ascending flow is formed. Has been done. Further, on the outside of the draft tube 130, an oblique downward flow toward the draft tube 130 is formed on the left side, and an upward flow is formed on the upper side on the right side, and the circulation flow is not formed as a whole.

As described above, if the distance between the main stirring blade 123 and the draft tube 130 is short and they are too close to each other, the main stirring blade 123 and the draft tube 130 interfere with each other, and a circulating flow is not formed.

Therefore, the crystallization reaction tank 50 according to the present embodiment needs to satisfy 1.1 <D / d with respect to the ratio D / d of the diameter D of the draft tube to the total length d of the main stirring blade 23.

FIG. 5 is a diagram showing parameter settings and simulation results of the crystallization reaction tank according to Comparative Example 2. FIG. 5A is a diagram showing an example of parameter setting of the crystallization reaction tank according to Comparative Example 2. As shown in FIG. 5A, in the crystallization reaction tank according to Comparative Example 2, when the total length of the main stirring blade 223 is d and the diameter of the draft tube 230 is D, D / d = 1. Set to 6. In this case, the distance between the tip of the main stirring blade 223 and the inner peripheral surface of the draft tube 230 is the draft and the tip of the stirring tank 23 of the crystallization reaction tank 50 according to the embodiment shown in FIG. 3 (a). It is wider than the distance between the tube 30 and the tube 30.

FIG. 5B shows the crystallization raw material 110 in the crystallization reaction tank according to Comparative Example 2 when the ratio D / d of the diameter D of the draft tube 230 to the total length d of the main stirring blade 223 is 1.6. It is the figure which showed the simulation result of the flow.

As shown in FIG. 5B, the ascending flow formed by the main stirring blade 223 changes its direction before reaching the upper end of the draft tube 30 and becomes a descending flow, and a circulating flow is generated in the draft tube 230. I have done it. As a result, the upward and downward flows are mixed in the draft tube 230. When such a flow occurs, the circulating flow does not occur in the entire crystallization reaction tank.

As described above, if the distance between the main stirring blade 223 and the draft tube 230 is too far, a circulating flow is generated inside the draft tube 230, and the circulating flow is not formed in the entire crystallization reaction tank.

Therefore, the crystallization reaction tank 50 according to the present embodiment needs to satisfy D / d <1.6 with respect to the ratio D / d of the diameter D of the draft tube to the total length d of the main stirring blade 23.

Considering both Comparative Examples 1 and 2, the crystallization reaction tank 50 according to the embodiment of the present invention has 1.1 <D with respect to the ratio D / d of the diameter D of the draft tube to the total length d of the main stirring blade 23. It is necessary to satisfy / d <1.6.

In order to form a stable circulating flow in the tank, it is desirable that the ratio D / d of the diameter D of the draft tube 30 and the total length d of the main stirring blade 23 is 1.2 or more and 1.5 or less. .. When D / d = 1.2 or less, as described in FIG. 4, there is a risk that the main stirring blade 123 and the draft tube 130 interfere with each other due to eccentricity of the stirring shaft or the like. On the other hand, when D / d = 1.5 or more, as described with reference to FIG. 5, there is a possibility that a circulating flow may be formed inside the draft tube 230.

FIG. 6 is a diagram showing the concentration distribution of solid particles in the crystallization reaction tank according to Comparative Examples 3 and 4 in which the draft tube is not provided. FIG. 6 (a) is a diagram showing the concentration distribution of solid particles in the entire crystallization reaction tank according to Comparative Example 3 in which a draft tube is not provided, and FIG. 6 (b) shows the bottom of FIG. 6 (a). It is an enlarged view. FIG. 6 (c) is a diagram showing the concentration distribution of solid particles in the entire crystallization reaction tank according to Comparative Example 4 in which the draft tube is not provided, and FIG. 6 (d) shows the bottom of FIG. 6 (c). It is an enlarged view.

In FIGS. 6A to 6D, regions A, B, C, and D are shown in descending order of concentration. As shown in FIGS. 6 (a) to 6 (d), when the draft tube 30 is not provided, the regions A to D are mixed in each place in the crystallization reaction tank. That is, it can be seen that there are variations in the concentration inside and at the bottom of the crystallization reaction tank, and there are variations in the particle size of the solid particles.

On the other hand, as described with reference to FIGS. 1 to 5, according to the crystallization reaction tank 50 and the crystallization classification device 100 according to the present embodiment, the draft tube 30 is provided around the main stirring blade 23, and the draft tube 30 is provided. By providing an auxiliary stirring blade 25 on the upper and outer sides of the draft tube 30 and appropriately setting the ratio D / d of the diameter D of the draft tube 30 to the total length d of the main stirring blade 23, a circulating flow circulating inside and outside the draft tube 30. Can be formed and the circulation speed can be increased, and the solid particles 111 having a desired particle size or larger can be efficiently deposited and discharged at the bottom of the tank while the crystallization reaction is efficiently carried out in the tank.

Although the preferred embodiments and examples of the present invention have been described in detail above, the present invention is not limited to the above-described embodiments and examples, and does not deviate from the scope of the present invention. Various modifications and substitutions can be added to the examples.

10 Stirring tank 20 Stirrer 21 Rotating shaft 22 Main stirring blade support 23 Main stirring blade 24 Auxiliary stirring blade support 25 Auxiliary stirring blade 26 Motor 30 Draft tube 35 Draft tube fixing jig 40 Obstacle plate 50 Crystallization reaction tank 60 Crystallization Raw material supply device 61 Crystallization raw material tank 62 Crystallization raw material input port 70 Classification outlet 100 Crystallization classification device 110 Crystallization raw material 111 Solid particles

Claims (3)

A stirring tank for holding the crystallization raw material and
A rotating shaft extending in the vertical direction in the stirring tank,
A draft tube provided so as to surround a predetermined depth region around the rotation axis, and
A first stirring blade fixed to the rotating shaft and provided in the draft tube,
It has a second stirring blade fixed to the rotating shaft and provided outside the draft tube.
The first stirring blade is provided in the draft tube so as to form an upward flow of the crystallization raw material.
The second stirring blade is provided above the draft tube so as to form a downward flow of the crystallization raw material outside the draft tube, and is supported by a support portion radially extending from the rotation axis. A crystallization reaction tank provided only on the outside of the draft tube in the radial direction. The crystallization reaction tank according to claim 1, wherein the first and second stirring blades are configured as inclined paddles. The crystallization reaction tank according to claim 1 or 2,
A crystallization raw material input port for supplying the crystallization raw material to the crystallization reaction tank, and
A crystallization classification device provided at the bottom of the crystallization reaction tank and having a classification outlet for discharging solid particles having a predetermined particle size or larger.

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