JP4521682B2 - Crystal grain size controller for crystallizer - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a crystal grain size control device for a crystallizer applied in relation to materials such as medical products, foods, optical products, electrical device materials, tape filler materials, and the like.
[0002]
[Prior art]
As a conventional crystallizer of this type, it comprises an evaporating part a disposed above and a crystallizing part b disposed below as shown in FIG. 10, and crystallized by convection of the raw material liquid into the crystallizing part b. There is known a device provided with a stirring means c for stirring at a predetermined fixed speed for promoting the growth.
[0003]
[Problems to be solved by the invention]
In the crystallization generation process, the crystal grows from the initial seed crystal process, which is the core of crystallization, to a crystal growth process in which the crystal grows further based on the seed crystal. According to the crystallizer, if stirring is simply performed at a relatively fast constant rotational speed for promoting the growth of crystals in the supersaturated raw material liquid by the stirring means, even if growing up to a large crystal, Some crystals break when collided with each other, with impingement blades, and with the tank wall, and when the growth is still accelerated by a fast stirring flow, the seed crystal process and the crystal growth process are not separated and mixed at the same time. The resulting crystallized crystals are polydispersed from small to large to form a wide distribution, making it difficult to crystallize into a unimodal distribution with a uniform particle size suitable for the application. There was a problem.
[0004]
An object of the present invention is to provide a crystal grain size control device for a crystallizer that solves these problems and enables formation of a unimodal distribution of crystal grain sizes with uniform crystal grain sizes.
[0005]
[Means for Solving the Problems]
In order to achieve the above-mentioned object, the present invention provides a stirring means capable of changing the rotation speed in the crystallization part of the crystallizer, and inputs information signals of the turbidity and concentration of the solution in the crystallizing part to rotate the stirring means. a step of promoting the generation of seed crystals to be crystallized nuclear activation solution to the speed to high speed, the steps of increasing the rate of production of seed by lowering the rotational speed to a high speed to low speed, the It is characterized by comprising control means for controlling by a control program of a process for promoting the growth of seed crystals and grown crystals by increasing the rotation speed from low speed to medium speed .
[0006]
DETAILED DESCRIPTION OF THE INVENTION
A first embodiment of the present invention will be described with reference to FIG.
[0007]
In FIG. 1, reference numeral 1 denotes a crystallization part of a crystallization apparatus, in which a crystal is produced from a raw material liquid 1b in a container 1a of the crystallization part 1 by a crystallization reaction. Although an evaporation unit for increasing the solution concentration is provided above 1, the evaporation unit may not be provided depending on the application.
[0008]
Reference numeral 2 denotes a stirring means provided in the crystallization unit 1, and the stirring means 2 includes a stirring blade 2a, a drive motor 2b for rotating the stirring blade 2a, and a drive circuit portion 2c thereof. The agitation flow can be varied by varying the rotational speed 2a by a control command of the control means described below.
[0009]
3 is a control means comprising a control unit such as a microcomputer, and 4 is a turbidity detecting means provided in the crystallization part 1 and comprising a light sensor in combination with a light emitting part 4a and a light receiving part 4b. The turbidity detected by is that the output of voltage or current varies depending on the number of crystals passing between the optical sensors 4a and 4b, so that the dispersed state of the crystals can be detected.
[0010]
Reference numeral 5 denotes an electric conductivity detecting means comprising an electric conductivity meter provided in the crystallization unit 1, and the concentration of the solution can be detected by detecting the electric conductivity of the solution with the electric conductivity meter. .
[0011]
Reference numeral 6 denotes a storage unit that stores a control program. The control unit 3 is connected to the storage unit 6 and to the drive circuit unit 2c of the stirring unit 2, and further includes the turbidity detection unit 4 The electrical conductivity detecting means 5 is also connected.
[0012]
Reference numeral 7 denotes a temperature detecting means including a thermistor temperature sensor provided in the crystallization unit 1, and 8 denotes a temperature adjusting means including an electric heater, etc. These temperature detecting means 7 and temperature adjusting means 8 are the control means 3. It is connected to the.
[0013]
Next, the operation of the first embodiment of the present invention will be described with reference to FIGS.
[0014]
The crystallization reaction is controlled by the temperature control system of the temperature detection means 7, the control means 3, and the temperature adjustment means 8 so that the raw material liquid 1b in the container 1a of the crystallization part 1 shown in FIG. , The concentration of the solute is increased to become supersaturated, and crystals are formed. The particle size of the crystals is greatly related to the stirring speed and the stirring time. FIG. 2 shows an example of a control program for controlling the stirring means 2. The vertical axis represents the rotational speed from high speed to low speed, the horizontal axis represents the time axis of each time point of the production reaction according to the concentration such as the saturated concentration or the supersaturated concentration, and the control means 3 includes the turbidity detection means 4 and the electric power The information on the dispersion state of the crystal and the concentration of the solute from the conductivity detecting means 5 is detected, and the rotational speed and stirring time of the stirring means 2 are variably controlled so as to follow the control program. A peak grain size distribution can be obtained.
[0015]
FIG. 3 shows a graph of the crystal grain size distribution, the vertical axis represents the weight for each crystal grain size, the horizontal axis represents the crystal grain size, and FIG. 4 shows the turbidity at each time point corresponding to the control by the control program of FIG. A graph is shown, and FIG. 5 also shows the electrical conductivity at each time point.
[0016]
FIG. 6 is a graph of the solubility curve of the solute in the crystallization formation process. The concentration is plotted on the vertical axis, the time axis is plotted on the horizontal axis, and the origin C ₀ , saturation concentration C ₁ points A, G, and nuclei are spontaneous. Spontaneous nucleation concentration in the supersaturated state generated C ₂ point B, E point, each point of D point near the maximum supersaturation concentration C ₃ shows the seed crystal that becomes the nucleus of crystallization when the concentration exceeds B point From the point B to the point E, a growth process in which a crystal grows based on the seed crystal and the nuclei seed crystal occurs at the same time depending on the conditions of growth promotion such as stirring. further increases, decreases the crystallization reaction the concentration of the solute to the G point as close as possible to saturation concentration C ₁ is ceased.
[0017]
Here, in order to control in accordance with the control program shown in FIG. 2, the control means 3 uses the information signals of the turbidity detection means 4 and the electrical conductivity detection means 5 shown in FIGS. If the set points corresponding to each time point A, B, D, E, and G shown in FIG. 5 are detected, the rotation speed of stirring is increased between A and B, and the activation of the solution promotes the generation of seed crystals. B, D between the increasing proportions of production of seed crystals is lowered because the high speed to the low speed traveling process of growing crystals on the basis of seed and seed crystal if there remains a high speed at the same time, from point D Slow concentration up to point E suppresses breakage of crystal grains, and from point E increases from low to medium speed to promote growth of seed crystals and growth crystals, and the change in the value of electrical conductivity is almost eliminated, so that saturation concentration C1 Is determined as the G point at which the crystallization reaction ends, especially between B and D and between D and E. It is possible to obtain a crystal grain size distribution of the unimodal shown in FIG. 3 by your.
[0018]
Next, a second embodiment of the present invention will be described with reference to FIGS.
[0019]
The second embodiment of the present invention was able to obtain a monomodal crystal grain size distribution in the first embodiment, but between B and E in the graph of the crystallization reaction process of FIG. For use in which the grain size of crystals is uniform by controlling the crystallization by separating the seed crystal generation process that forms the nucleus of the crystal to be generated and the crystal growth process in which the crystal grows based on the seed crystal into two temperature zones. It is a feature that optimum crystal grains can be obtained.
[0020]
The apparatus used in the second embodiment of the present invention is exactly the same as that shown in FIG. 1, and the crystallization reaction concentration is cooled to a specific temperature zone and, for example, 10 ° C. lower than the specific temperature zone. Crystallize by adjusting to the two stages.
[0021]
First, in order to produce a seed crystal, the raw material liquid is adjusted to a specific temperature, and the crystallization reaction is performed by controlling the stirring as in the case of the first embodiment, and the graph of the crystallization reaction process of FIG. Between B, D, and E, a seed crystal that is the nucleus of crystallization and a part of the crystal that grows based on the nuclear seed crystal are formed, and the solute concentration is lowered to the spontaneous nucleation concentration C ₂ . Further, from the point before the point G approaching the saturated concentration C ₁ , next, for example, when cooling with stirring at medium to high speed rotation so as to lower the temperature by 10 ° C., the concentration decreased to the concentration close to the saturated concentration C ₁ . The solute concentration again becomes supersaturated, and the crystallization reaction process up to points A, B, D, E, and G shown in FIG. 6 is repeated with stirring control, and the crystal grain size of FIG. The seed crystals and some of the grown crystals shown in the distribution graph are As a new seed crystal, the seed crystal and the growth crystal are used as a crystal grain size distribution graph shown in FIG. 8 to obtain a growth crystal in which the crystal weights of several grain sizes are increased. The crystal is separated into these two temperature zones. By controlling the deposition reaction, it is possible to obtain crystal grains suitable for applications having uniform crystal grain sizes.
[0022]
Further, a third embodiment of the present invention will be described with reference to FIG.
[0023]
In the third embodiment of the present invention, even when the solution concentration at which the crystallization reaction ends in the first or second embodiment, the control for increasing the concentration of the solution is continued. The feature is that the diameter can be further increased.
[0024]
The apparatus used in the third embodiment of the present invention is exactly the same as that shown in FIG. 1, and lowers the solution temperature in the crystallization part 1 even when the saturation concentration at which the crystallization reaction ends is reached. Alternatively, in the case where an evaporation section is provided, the solvent can be evaporated to make the concentration again a supersaturated concentration at which crystallization reaction is possible, and the saturation concentration C ₁ of the solubility curve graph of the solute of FIG. The crystallization reaction once stops at the G point of the crystal, but the saturation concentration of the graph added in FIG. 9 decreases to C ₁ ′ due to the temperature decrease or evaporation, and the G ′ point becomes a new saturation concentration, and the crystallized crystal Further grows to a large particle size up to the point G ′.
[0025]
When the process is performed up to the point G ′, the concentration is increased again, the new saturation concentration is decreased to C _{1 ″,} and the crystallization reaction is repeated up to the point G ″ to further increase the crystal grains.
[0026]
Thus, the crystal grain size can be further increased by continuing the control for increasing the concentration.
[0027]
The control for increasing the concentration may be performed not only at the saturated concentration point G but also at the time of the supersaturated concentration state from the point A to the point G.
[0028]
【The invention's effect】
Thus, according to the present invention, the turbidity and concentration information signal in the crystallization part is input, and the control means controls the rotation speed and the stirring time of the stirring means, so that the grain size of the unimodal distribution is obtained. It has the effect of obtaining crystal grains with uniform grain sizes.
[Brief description of the drawings]
FIG. 1 is a system configuration diagram of a first embodiment of this invention.
FIG. 2 is a graph of a control command program for the stirring means.
FIG. 3 is a distribution graph of crystal grain size.
FIG. 4 is a graph of the turbidity detection signal.
FIG. 5 is a graph of a detection signal of the electrical conductivity.
FIG. 6 is a graph of a solubility curve of a solute during a crystallization generation process.
FIG. 7 is a distribution graph of crystallization particle size in a specific temperature zone according to the second embodiment of the present invention.
FIG. 8 is a distribution graph of crystal grain size in the cooling temperature zone.
FIG. 9 is a graph of a solubility curve of a solute in the third embodiment of the present invention.
FIG. 10 is an explanatory diagram of a conventional crystallization apparatus.
[Explanation of symbols]
DESCRIPTION OF SYMBOLS 1 Crystallization part 1a Container 1b Raw material liquid 2 Stirring means 2a Stirring blade 2b Drive motor 2c Drive circuit part 3 Control means 4 Turbidity detection means 4a Light emission part 4b Light reception part 5 Conductivity detection means 6 Storage part 7 Temperature detection means 8 Heating means

Claims (5)

A stirrer capable of varying the rotation speed is provided in the crystallization part of the crystallizer, and the information signal of the turbidity and concentration of the solution in the crystallizer is input to increase the rotation speed of the stirrer and activate the solution. a step of promoting the generation of seed crystals serving as crystallization nuclei, and the process of increasing the rate of production of seed by lowering the rotational speed to a high speed to low speed, raising the medium speed the rotational speed from a low speed A crystal grain size control device for a crystallizer equipped with a control means for controlling by a control program for a process for promoting the growth of seed crystals and grown crystals. 2. The crystal grain size control device for a crystallization apparatus according to claim 1, wherein a turbidity detection means comprising an optical sensor is provided in the crystallization part. The electrical conductivity detection means is provided in the crystallization part, and the control means inputs a detection signal of the electrical conductivity detection means to detect the solution concentration in the crystallization part. The crystal grain size control device of the crystallizer. The crystallization part is provided with a temperature detecting means and a temperature adjusting means, and the control means grows a crystal based on a predetermined seed crystal generation temperature zone for generating a seed crystal serving as a nucleus of crystallization and the seed crystal. The crystal grain size of the crystallizer according to any one of claims 1 to 3, wherein the crystal grain size is controlled by separating and crystallizing in two different temperature zones from a predetermined crystal growth temperature zone. Control device. The control means performs control to increase the crystal grain size of the crystallization by continuing control to increase the concentration of the solution in the crystallization part by adjusting the temperature or evaporating the solvent. The crystal grain size control apparatus of the crystallizer of any one of thru | or 4.

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