JPS6150001B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a tank-type cooling crystallizer. More specifically, the present invention relates to a crystallizer in which the surface of a flexible synthetic resin tube is used as a cooling surface, and crystals are not deposited on the cooling surface which is moved up and down while twisting the synthetic resin tube inside a crystallization tank.

Conventionally, crystallization by cooling has been used as a method for extracting a substance as crystals from a solution containing a substance whose solubility varies greatly depending on temperature.

As a cooling crystallizer for this purpose, a crystallizer that cools from the side wall of the crystallizer is widely used, but in such a crystallizer with a fixed cooling surface, the part with the highest degree of supersaturation is cooled. This is the surface of a cooling surface, and scaling tends to occur on that surface, so it is often necessary to remove crystals that have crystallized on the surface of the cooling surface. In order to avoid the precipitation of crystals on the surface of the cooling surface, for example, the cooling surface and the liquid to be cooled may have a large relative velocity to make it difficult for crystals to precipitate on the cooling surface, or the liquid to be cooled and the cooling surface may A method has been adopted to make it difficult for crystals to precipitate by keeping the temperature difference small. However, in order to provide a large relative velocity between the cooling surface and the liquid to be cooled, a transfer means such as a high-speed stirring blade or a large-capacity pump is required, and the temperature difference between the cooling surface and the liquid to be cooled is also reduced. If it is made small, a very large cooling area is required.
Another method is to provide a scraper and mechanically scrape off the crystals deposited on the cooling surface, but this requires a complicated device and is likely to cause mechanical troubles.

Furthermore, in contrast to the conventional crystallizer with a fixed cooling surface, a crystallizer with a rotating cooling surface in which a hollow plate with a refrigerant passed inside is rotated has been proposed (Japanese Patent Application Laid-Open No. 1989-1999).
−43051). However, although the precipitation of crystals on a rotating flat cooling surface is considerably suppressed compared to a fixed cooling surface, the precipitation of crystals on a cooling surface cannot be avoided. It is necessary to scrape off the crystals deposited on the surface.

None of these methods can completely prevent problems caused by precipitation of crystals on the cooling surface, and furthermore, the apparatus becomes larger or more complex.

As a result of research on a crystallizer that does not have such drawbacks and does not cause precipitation of crystals on the cooling surface, the present inventor has found that the surface of a flexible synthetic resin pipe is used as the cooling surface,
By applying twisting rotation and vertical motion to the synthetic resin tube, we have completed a crystallizer in which the deposited crystals do not adhere to the cooling surface.

The crystallizer of the present invention is a cooling tube in which a refrigerant is passed through a flexible synthetic resin tube, and the synthetic resin tube is installed vertically in a U-shape to form a U-shaped tube. By reciprocating up and down, and twisting the bottom part back and forth, it prevents crystals from adhering to the surface of the U-shaped tube, which is the cooling surface.

FIG. 1 is a sectional view showing an example of the apparatus of the present invention, where 1 is a crystallization tank and 2 is a cooling pipe body (synthetic resin tube bundle in the embodiment). A rotating shaft 3 that reciprocates is provided in the center of the crystallization tank 1, and this rotating shaft 3 has a bearing 1 composed of an upper rotating shaft 3' and a lower rotating shaft 3''.
2, 13, 14, and 15. The bearing 12 is attached to the upper lid of the crystallization tank, and the bearing 13 is attached to the stay 16 attached to the upper lid. Further, the bearings 14 and 15 are mounted on stays 19 and 20 within a cone 18 supported by a stay 17 inside the crystallization tank.

A collar 21 to which the horizontal support rod 4 is fixed is loosely fitted to the upper rotating shaft 3', and a pin guide groove 5 is formed in the collar 21 to fit a pin 22 installed on the upper rotating shaft 3'. ing. One end of the horizontal support rod 4 is loosely engaged with a vertical guide 4' so that it can move only in the vertical direction.

On the other hand, the upper rotating shaft 3' and the lower rotating shaft 3'' are coupled in a collar 33 fixed to the upper rotating shaft 3' so that the lower rotating shaft 3'' can rotate relative to each other. Since the ends of the two are fitted in the shape shown in FIG. 2, there is some play in the rotation of the 3' and 3'' axes.

Thus, when the 3′ axis rotates back and forth through 180°, 3″
The shaft is arranged at an angle of 90 degrees, that is, the rotation of the lower rotary shaft 3'' relative to the upper rotary shaft 3' is approximately 1/2.

Both ends of the bundle 2 of synthetic resin tubes bent into a U-shape are fixed to the horizontal support rod 4 set as described above by fixing members 23, and the bottom of the bundle is fixed to the lower rotating shaft 3'' by a fixing member 24. Flexible tubes 6 for passing the refrigerant are connected to both ends of the bundle 2 of synthetic resin pipes installed in this manner via connectors 25.

Thus, when the upper rotating shaft 3' rotates about 180 degrees counterclockwise when viewed from above, the collar 21 is pushed upward by the pin 22, and as a result, the horizontal support rod 4, that is, both ends of the bundle of synthetic resin tubes 2 is raised by the height of the guide groove 5 of the collar 21. Also, since the lower shaft rotates about 90 degrees, the bundle 2 of synthetic resin tubes rotates while being stretched. Similarly, the upper rotating shaft 3'
When it rotates clockwise, the opposite phenomenon to that described above occurs, and the horizontal support rod 4 descends and the lower rotating shaft 3'' rotates in the opposite direction, causing the bundle of synthetic resin tubes 2 to twist and rotate while being slackened. This is what we do.

The crystallization tank 1 includes a supply nozzle 7 attached to the upper lid and/or a supply nozzle 7' attached to the side surface of the central part, an overflow port partition plate 26 on the inner surface of the upper part,
An overflow port 9 is provided on the upper side, an outlet 8 is provided on the lower side, and a blow-up nozzle 28 for classification is provided at the center of the lower portion.

The raw material is thus transferred to nozzle 7 and/or nozzle 7'
The liquid is supplied more continuously and is cooled and crystallized by the bundle of synthetic resin tubes 2, which is a cooling tube, and the liquid with a lower concentration of crystalline components flows out from the overflow port 9 and becomes higher in concentration. The liquid is taken out from the slurry outlet 8.

The liquid flowing out from the overflow port 9 is injected into a nozzle 28 by a pump 27 and used for classification.

After the fine crystals floating in the liquid are extracted from the overflow port 9 and dissolved in the heater 29, some of the liquid is taken out through the tube 31 from the bottom of the classification leg 30, and the remaining part is If necessary, the liquid is returned to the crystallization tank 1 from the side of the crystallization tank through the pipe 32, and an upward flow is applied to the tank so that only large crystals can be taken out as a slurry.

The aforementioned rotating shaft is divided into an upper rotating shaft 3' and a lower rotating shaft 3'', which are connected by a coupling with a play of 90 degrees, but this is due to a design problem of the pin guiding groove of the collar 21. This is related to the above, and it is also possible to use only one rotating shaft without such a coupling.

The point is that the upper end of the synthetic resin tube bundle should move up and down, and the lower end should twist and turn, so any design can be selected for this purpose.

In the present invention, the synthetic resin constituting the cooling pipe body 2 may be any flexible resin, such as polytetrafluoroethylene, polytetrafluoroethylene,
A material with high mechanical strength such as a copolymer of tetrafluoroethylene and hexafluoropropylene is preferable, but
It may also be polyvinyl chloride, polyethylene, polypropylene, etc. It is preferable to use a tube bundle consisting of a large number of thin tubes for this cooling tube body in order to increase the heat transfer area. This thin tube is preferably as thin as possible within a range that allows the refrigerant to pass smoothly through the inside, and specifically, one with an outer diameter of 2.5 to 6.4 mm is used.

When performing cooling crystallization using such an apparatus of the present invention, a liquid to be crystallized is placed in the crystallization tank 1, and the cooling tube body 2 is reciprocated while passing the coolant through the flexible tube 6. Rotate. The reciprocating rotation of the cooling pipe body is performed by converting the rotation of the motor 10 into reciprocating rotation by a converter 11. The rotation angle of the rotating shaft 3 is different between the upper and lower parts, and the angle of rotation is 90 to 180° at the upper part, preferably about 180° at the lower part, and about 1/2 of that at the lower part. Since the support rod moves up and down as it rotates, the cooling pipe body is given vertical movement and twisting rotation, so that crystals do not adhere to the surface of the cooling pipe body.
The crystals precipitated by cooling settle to the bottom of the crystallization tank and are extracted from the crystal outlet at the bottom of the tank. When crystallizing continuously, the liquid to be crystallized may be continuously supplied from the upper and/or lower sides of the tank, and the liquid with a lower concentration of crystalline components may overflow from the upper part.

The cooling surface of the device of the present invention is a tube made of synthetic resin, and since it is entirely curved and constantly subject to vertical movement and twisting rotation, crystals will adhere to the cooling surface even during long-term continuous operation. Never.

The apparatus of the present invention can be applied to crystallization of various substances. For example, caustic soda crystallization for removing salt from a caustic soda aqueous solution containing salt;
Alternatively, it can be used to separate isomers of dichlorobenzene or dichlorophenol, and crystals do not precipitate on the cooling surface, and crystallization can be performed continuously for a long time or repeatedly in batches.

Example Paradichlorobenzene 65
Para-dichlorobenzene crystals were precipitated from a liquid containing 35% by weight of ortho-dichlorobenzene. At this time, the cooling pipe body was subjected to a reciprocating rotational movement at a rotation angle of 180° at the top and 90° at the bottom at a rate of 20 reciprocations/min. The temperature of the brine passed through the cooling pipe body is -10°C.

Put 100% of the above liquid to be cooled into the crystallization tank, rotate the cooling pipe body back and forth to bring the temperature to 5℃, and then pour the liquid to be cooled at 60℃.
A slurry containing 40% paradichlorobenzene crystals with an average particle size of 0.55 mm was extracted from the bottom of the tank at a rate of 10 kg/h.

As a result of continuous operation for 6 hours, almost no crystal precipitation was observed on the surface of the cooling pipe body of the moving part.

[Brief explanation of the drawing]

FIG. 1 is a cross-sectional view showing one example of the device of the present invention, and FIG. 2 is an end view of the connecting portion of the vertical rotation shaft shown in FIG. DESCRIPTION OF SYMBOLS 1... Crystallization tank, 2... Cooling pipe body, 3... Rotating shaft, 4... Support rod, 5... Guideway, 6... Flexible tube, 7... Cooled liquid supply port, 8...
Crystal outlet.

Claims (1)

[Claims] 1. A horizontal support member is provided in the upper part of the crystallization tank to reciprocate up and down while interacting with a vertical shaft, and a synthetic resin pipe is made into a U-shape and its upper ends are The bottom of the U-shaped synthetic resin pipe is fixed to a horizontal support member below the vertical shaft, and both ends are configured to allow refrigerant to pass therethrough.As the vertical shaft reciprocates, both ends of the U-shaped synthetic resin tube move vertically and reciprocally. is a crystallizer characterized by reciprocating twisting rotation. 2. The crystallizer according to claim 1, wherein the vertical axis is composed of two upper and lower axes, and the upper vertical axis and the lower vertical axis are connected with play.