JP3598692B2 - Crystallization method and crystallizer - Google Patents

Description

[0001]
TECHNICAL FIELD OF THE INVENTION
The present invention relates to a crystallization method and an apparatus suitable for the method, and more particularly, to a method for cooling and crystallizing a solution containing a crude crystallizable substance by latent heat of evaporation of a solvent, and an apparatus suitable for the method. .
[0002]
[Prior art]
A method of evaporating a solvent from a solution containing a crude crystallizable substance while stirring under reduced pressure to crystallize the crystallizable substance is known. For example, Japanese Patent Application Laid-Open No. 58-104603 discloses that a solution containing a crystallizable substance is concentrated using a crystallizer of a type in which a solvent is evaporated by heating to concentrate the crystallizable substance. A method for performing precipitation, in which a draft tube is used as a stirrer, the inner wall of a gas phase part at the top of a crystallizer for stirring a liquid in a vertical direction is cooled, and a part of the evaporated solvent is condensed and flows down to the inner wall. And a crystallization method for forming a wet surface. In this method, most of the evaporated solvent is distilled out of the crystallization vessel.
[0003]
[Problems to be solved by the invention]
However, in a crystallization vessel provided with a stirrer having a stirring axis in the center of the vessel, the scale of the crystallizable substance is more easily generated on the stirring axis of the gas phase than on the inner wall surface of the gas phase of the vessel. The scale peels off and falls during the crystallization operation and mixes into the solid-liquid mixture obtained after crystallization, lowering the purity of the crystallizable substance or blocking the outlet provided at the lower part of the crystallization vessel However, there is a problem that operability is deteriorated.
[0004]
[Means for Solving the Problems]
The present inventors have conducted intensive studies to solve the above-described problems, and as a result, when cooling the coarsely crystallizable substance-containing supersaturated solution and crystallizing the crystallizable substance, the cooling is performed when the solvent evaporates. Utilizing the latent heat of, the evaporated solvent is condensed outside the crystallization vessel, and the method of spraying the condensed solvent into the gas phase of the crystallization vessel has been found to prevent the formation of scale. Having found a suitable device, the present invention has been completed.
That is, the present invention relates to a method for crystallizing a crystallizable substance by cooling a supersaturated solution containing a crude crystallizable substance while stirring it using a stirrer having a stirring axis in a crystallization vessel. And evaporating the solvent under reduced pressure, cooling the supersaturated solution by the latent heat thereof, condensing the evaporated solvent outside the crystallization vessel, and spraying this to the gas phase in the crystallization vessel. A crystallization method characterized by: (ii) evaporating the solvent from the solution containing the crude crystallizable substance under reduced pressure while stirring, and cooling the solution by the latent heat of the evaporation to remove the crystallizable substance; A crystallization device,
a) The apparatus has a crystallization vessel C, a condenser E, a storage tank T, a liquid feeder P, and a vacuum source V,
b) The crystallization vessel C has a lid H, a cylindrical part D, and an outlet Q for the crystallized mixture at the bottom in the upper part in the height direction,
c) Further, the crystallization vessel C has a stirrer A at the center thereof, a driving device K above the stirrer A, and a sprayer S above the cylindrical part D and near the stirrer A,
d) The stirrer A has a stirring shaft F and a stirring blade I integrally attached to a lower portion of the stirring shaft F,
e) the lid H has an opening O ₄ for inserting the opening O ₁ and the raw material supply port O ₂ for inserting the stirring shaft F the outlet O ₃ and sprayer S,
f) A valve B is attached to the outlet Q,
g) condenser E has an inlet E ₁ of evaporated solvent, and outlet E ₂ of the condensed solvent, the outlet E _3,
(1) The crystallizer vessel C and the condenser E, via the inlet E ₁ solvent evaporated and the exhaust port O _3, linked by evaporation line L _1,
(2) the condenser E and a crystallizer vessel C, and the outlet E _2, a line L ₃ of the condensate connecting inlet of the conductor outlet E ₂ and storage tank T, a reservoir T,該貯Tomeso a feed line L ₄ connecting the inlet of the outlet and feeding machine P T, then the liquid feeding device P, a reflux line L connecting the outlet and sprayer S of said transmission fluid machine P, via the sprayer S, tied And
(3) In addition, the condenser E and the vacuum source V, through the vacuum line L ₂ outlet E ₃ above, there is provided a crystallization apparatus characterized by comprising tied .
Hereinafter, the present invention will be described in detail.
[0005]
BEST MODE FOR CARRYING OUT THE INVENTION
In crystallizer of the present invention, stirring shaft F of agitator A is passed through the insertion opening O ₁ of the lid H and extends to the outside above the crystallizer vessel C, above the crystallizer vessel C, for example , Is rotationally driven by a driving device K installed near the upper end of the stirring shaft F. A stirring blade I is integrally attached to a lower portion of the stirring shaft F.
Examples of the stirring blade I include an anchor blade, an anchor blade with paddle blades, a flat paddle blade, an inclined paddle blade, a paddle blade for high viscosity, an impeller blade, and the like.
Examples of the condenser E include a heat exchanger and the like.
Further, as a preferable liquid feeder P, for example, a pump having no pressure fluctuation, such as a spiral pump, may be mentioned.
[0006]
The crystallization method of the present invention is carried out in a batch format, and preferable crystallizable substances include industrial products such as fragrances, pharmaceuticals and agricultural chemicals, and organic compounds useful as intermediates thereof. Preferred examples of the solvent include organic solvents such as alcohols, ethers, and hydrocarbons.
The evaporation of the solvent in the crystallization method of the present invention is preferably performed by reducing the degree of pressure reduction in the crystallization vessel C several times, and more preferably by gradually reducing the pressure in the crystallization vessel C.
[0007]
In the crystallization method of the present invention, the evaporated solvent is condensed in the condenser E provided outside the crystallization vessel C of the above apparatus. The condensed solvent is temporarily stored in a storage tank T such as a tank, and then returned to the crystallization vessel C using a liquid feeder P such as a pump.
As described above, by using the apparatus of the present invention, the amount of the solvent in the crystallization vessel C can be made substantially constant.
By making the amount of the solvent in the crystallization vessel C substantially constant, in evaporative crystallization, for example, a decrease in purity of the crystallizable substance due to concentration of impurities contained in the crude crystallizable substance is prevented. can do. Further, in the pre-process of the method of the present invention described later, for example, crystal nuclei can be easily generated by cooling.
[0008]
Hereinafter, the device of the present invention will be described in more detail with reference to the drawings.
A central portion in the height direction of the crystallization vessel C of the apparatus of FIG. 1 is a cylindrical portion D, and an upper portion of the cylindrical portion D is a lid H. Further, the lower side of the cylindrical portion D has an arc shape that tapers downward. An outlet Q for the solid-liquid mixture after crystallization is provided in a small-diameter cylindrical shape at the lowermost end of the arc, and a valve B is attached to the outlet Q.
Further, a jacket J is provided outside the cylindrical portion D, and a coolant or a heat medium can be circulated as needed.
The lid H, the gas phase G of the crystallizer vessel C, and outlet O ₃ is provided for communicating to a vacuum source V, such as a vacuum pump, during the exhaust port O ₃ and the vacuum source V Is provided with a condenser E such as a heat exchanger for condensing the evaporated solvent.
In addition, the said lid H, in addition to the outlet O _3, nebulizer S of the opening O _1, the raw material supply port O ₂ and a shower or the like for inserting the stirring shaft F fitted with stirring blades I impeller type opening O ₄ or the like for insertion are provided. The evaporated solvent through evaporation line L ₁ through the exhaust port O _3, is introduced into the inlet E ₁ of evaporated solvent in a condenser E, then is condensed in condenser E. Condensed solvent exits the condenser outlet E ₂ of the condensed solvent E, through the inlet-side valve (not shown) of the storage tank T such as a line L ₃ and the tank of the condensate, once reservoir Accepted by T. The solvent exiting the outlet side valve (not shown) of the storage tank T is lead to feeding machine P such as a pump via a feed line L _4. Next, the liquid is sent to the sprayer S in the crystallization vessel C through the reflux line L by the liquid feeder P. The sent solvent is sprayed by the sprayer S over the entire gas phase portion G of the cylindrical portion D.
[0009]
By adopting such a configuration, it is possible to perform a pre-process of the below-described evaporative crystallization of the present invention and the evaporative crystallization of the present invention continuously by the same apparatus.
[0010]
Prior to performing the evaporative crystallization according to the present invention, a saturated solution or a solution slightly supersaturated with the saturated solution is prepared. Preferably, a seed crystal is further added after the preparation of these solutions, or the prepared solution is cooled or concentrated to generate crystal nuclei, and a supersaturated solution (slurry) in which the seed crystals or crystal nuclei are present is used. An obtaining step is performed.
Hereinafter, these pre-processes will be described in detail.
First, from the raw material supply port O ₂ provided in the lid H of the crystallizer vessel C, it supplies the crude crystals segregation material and crystallization solvent, followed by stirring. From the solution obtained, a saturated solution or a solution of a crystallizable substance which is slightly more supersaturated than the saturated solution is prepared as shown in (i) below. A slurry in which a seed crystal or a crystal nucleus is present in a supersaturated solution is obtained as shown in (ii) below.
(I) The above-mentioned saturated solution or a solution slightly supersaturated than the saturated solution is prepared by cooling or concentrating the solution obtained by stirring the crystallizable substance and the crystallization solvent. Is
In the case of cooling, a method of passing a refrigerant through the jacket J under normal pressure, or evaporating the solvent under reduced pressure, cooling is performed using latent heat when the solvent evaporates, and the evaporated solvent is removed from the container. It is carried out by a method of refluxing into the container after condensing outside.
In the case of concentration, the solvent is evaporated under reduced pressure.
(Ii) {circle around (1)} When the slurry is obtained, the temperature of the solution in the crystallization vessel C is, for example, a temperature corresponding to a state where the concentration of the crystallizable substance is slightly more than the saturated solution (hereinafter referred to as t ₂ ° C). When the pressure at t ₂ ° C becomes p ₂ torr), a seed crystal of a crystallizable substance is added. The seed crystal may be a powder or a slurry suspended in a small amount of a solvent. The amount of the seed crystal to be added is appropriately adjusted depending on the desired size of the crystal obtained after crystallization.
{Circle over (2)} Instead of adding seed crystals to the above-mentioned saturated solution or a solution in a slightly supersaturated state, crystal nuclei may be formed from these solutions. The generation of crystal nuclei is performed, for example, by further cooling the slightly supersaturated solution under normal pressure, or evaporating the solvent under reduced pressure, and cooling is performed using latent heat when the solvent evaporates, and the evaporated solvent Is evaporated by evaporation outside the container and then refluxed into the container.
[0011]
Next, the crystallization method of the present invention will be described in detail.
[0012]
The evaporation crystallization of the present invention is preferably performed using a slurry obtained after the addition of seed crystals or the generation of crystal nuclei.
In this case, the evaporation crystallization is performed under reduced pressure from the slurry (ii) (1) obtained by adding a seed crystal or the slurry (ii) (2) obtained by generating crystal nuclei. The solvent in the slurry is evaporated, and the latent temperature at that time is used to raise the liquid temperature to a predetermined temperature (hereinafter referred to as t ₁ ° C; the pressure at t ₁ ° C is referred to as p ₁ torr). This is done by gradually lowering it.
Evaporated solvent reaches the condenser E through outlet O ₃ and evaporation line L ₁ of the cover H, is condensed here. The condensed solvent is received in the storage tank T. The solvent stored in the reservoir T, through feed line L _4, leading to feeding machine P. Next, this solvent is intermittently or continuously sent from the reflux line L to the sprayer S in the crystallization vessel C by the liquid feeder P. In the illustrated example, the sprayer S is configured by a shower including a rotary cleaning nozzle.
This shower has passed through reflux line L and the communication that is inserted into the insertion opening O ₄ of the lid H, an upper portion of the cylindrical portion D, and and provided in the vicinity of the stirring shaft F.
In order to more effectively prevent the scaling, the spray liquid from the sprayer S is sprayed over the entire gas phase portion G of the cylindrical portion D, particularly, mainly around the stirring shaft F so as to spray the spray liquid from the sprayer S. It is preferable to adjust the type, the flow rate of the liquid feeder P, and the like.
After lowering the liquid temperature and the pressure until the predetermined temperature t ₁ ° C and the pressure p ₁ torr are reached, stirring is continued under the same conditions for a while. During a series of evaporative crystallization operations, the solvent condensed in the condenser E passes through the condensate liquid line L ₃ , the storage tank T, the liquid feed line L ₄ , the liquid feeder P, and the reflux line L to form the cylindrical portion D. The whole of the gas phase G is sprayed from the sprayer S. Next, after returning to normal pressure, the valve B is opened, and the solid-liquid mixture after evaporation crystallization is collected from the outlet Q.
[0013]
【Example】
Next, the present invention will be described with reference to examples, but the present invention is not limited by these examples. In the examples,% indicates% by weight.
[0014]
Example 1
Using the apparatus shown in FIG. 1 (capacity: 1 m ³ ), a supersaturated methanol solution of crude coumarin containing about 50% coumarin was crystallized by evaporation. The solid-liquid mixture after the precipitation was taken out. Liquid temperature t ₂ when seeded coumarin is about 35 ° C., the t ₁ was about 15 ° C.. Further, _{p 2} is about 170torr, _{p 1} was about 70 torr. As shown in FIG. 1, the condensed methanol was sprayed downward in a range of an angle of 180 ° with respect to the crystallization vessel C, and the sprayed liquid reached a maximum of about 1.5 m.
During evaporation crystallization, no scaling was observed on the inner wall surface of the vessel of the gas phase part G or the stirring axis F.
Incidentally, a supersaturated solution of the crude coumarin, a mixture of crude coumarin and methanol supplied from the raw material supply port O ₂ heated, dissolved to give a methanol solution, then the methanol solution, the methanol was evaporated under reduced pressure and concentrated By doing, it was obtained.
[0015]
Comparative Example 1
As shown in FIG. 2, evaporation and crystallization were performed in the same manner as in Example 1 except that methanol condensed in the condenser E was intermittently refluxed to the liquid phase portion N using the dropping tube M.
As shown in FIG. 3, the scaling of the crystal was conspicuous in the gas phase portion G, particularly in the stirring axis F.
[0016]
【The invention's effect】
ADVANTAGE OF THE INVENTION According to the method of this invention, the scaling of the crystal | crystallization to the stirrer of the gaseous-phase part of a crystallization container or the inner wall of a cylindrical part can be prevented easily.
Further, according to the apparatus of the present invention, in the evaporative crystallization, when the solvent condensed outside the crystallization vessel is refluxed to the crystallization vessel, the refluxed solvent is transferred to the entire gas phase portion of the crystallization vessel cylinder. Can be easily sprayed.
[Brief description of the drawings]
1 is a schematic longitudinal sectional view of an apparatus of the present invention; FIG. 2 is a schematic longitudinal sectional view of an apparatus of Comparative Example 1; FIG. 3 is an enlarged view of a gas phase part of the apparatus of FIG. 2;
A stirrer, B valve, C crystallization vessel, D cylindrical part, E condenser, F stirring shaft, G gas phase part, H lid, I stirring blade, J jacket, K ─Drive device, L─ reflux line, L ₁ ─evaporation line, L ₂ ─vacuum line, L ₃ ─condensate line, L ₄ ─liquid feed line, M─dropping line, N─liquid phase portion, O ₁ ─ Opening, O ₂ ─ raw material supply port, O ₃ ─ exhaust port, O ₄ ─ insertion port, P─ liquid feeder, Q─ outlet, S─ sprayer, T─ storage tank, V─ vacuum source

Claims (2)

A method of crystallizing a crystallizable substance by cooling a supersaturated solution containing a crude crystallizable substance while stirring using a stirrer having a stirring axis in a crystallization vessel, and evaporating the solvent under reduced pressure. Cooling the supersaturated solution with the latent heat, condensing the evaporated solvent outside the crystallization vessel, and spraying the condensed solvent into the gas phase in the crystallization vessel. A device for evaporating the solvent from the solution containing the crude crystallizable substance under reduced pressure with stirring, cooling the solution by the latent heat of the evaporation, and crystallizing the crystallizable substance,
a) The apparatus has a crystallization vessel C, a condenser E, a storage tank T, a liquid feeder P, and a vacuum source V,
b) The crystallization vessel C has a lid H, a cylindrical part D, and an outlet Q for the crystallized mixture at the bottom in the upper part in the height direction,
c) Further, the crystallization vessel C has a stirrer A at the center thereof, a driving device K above the stirrer A, and a sprayer S above the cylindrical part D and near the stirrer A,
d) The stirrer A has a stirring shaft F and a stirring blade I integrally attached to a lower portion of the stirring shaft F,
e) the lid H has an opening O ₄ for inserting the opening O ₁ and the raw material supply port O ₂ for inserting the stirring shaft F the outlet O ₃ and sprayer S,
f) A valve B is attached to the outlet Q,
g) condenser E has an inlet E ₁ of evaporated solvent, and outlet E ₂ of the condensed solvent, the outlet E _3,
(1) The crystallizer vessel C and the condenser E, via the inlet E ₁ solvent evaporated and the exhaust port O _3, linked by evaporation line L _1,
(2) the condenser E and a crystallizer vessel C, and the outlet E _2, a line L ₃ of the condensate connecting inlet of the conductor outlet E ₂ and storage tank T, a reservoir T,該貯Tomeso a feed line L ₄ connecting the inlet of the outlet and feeding machine P T, then the liquid feeding device P, a reflux line L connecting the outlet and sprayer S of said transmission fluid machine P, via the sprayer S, tied And
(3) In addition, the condenser E and the vacuum source V, through the vacuum line L ₂ outlet E ₃ of the, crystallization apparatus characterized by comprising tied.

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