AU2000265984B2

AU2000265984B2 - Apparatus for purification of crystal and method

Info

Publication number: AU2000265984B2
Application number: AU2000265984A
Authority: AU
Inventors: Akihiro Ito; Kentaro Otawara; Ryoichi Watanabe
Original assignee: Kureha Corp; Kureha Techno Engineering Co Ltd
Current assignee: Kureha Corp; Kureha Techno Engineering Co Ltd
Priority date: 1999-08-23
Filing date: 2000-08-22
Publication date: 2004-12-16
Anticipated expiration: 2020-08-22
Also published as: AU6598400A; JP4354582B2; JP2001058103A; WO2001014290A1

Description

1 APPARATUS AND METHOD OF REFINING CRYSTAL TECHNICAL FIELD The present invention relates to an apparatus and method of refining a crystal by counterflow-contact between a crystal material and a melted liquid containing a refined crystal component.

BACKGROUND ART Among various types of apparatuses for refining crystals, Japanese Patent Application Kokoku number 47- 40621 discloses a refining apparatus using a melted liquid that contains crystal component. As shown in Fig. 3, this conventional upright type apparatus comprises, at a lower part thereof, an inlet 12 having a screw conveyer 13 therein to supply a crystal material or crude crystal that includes impurities, and, at an upper part thereof, a melting heater 14 to melt the crystal material. The liquid melted by the heater 14 are brought into counterflowcontact with the crystal material moved upwardly in the refiner 11 from the inlet 12 to refine the crystal material.

The refined crystal is taken out from an outlet 15 provided at an upper part of the refiner 11. An agitator 18 of the refiner 11 is provided with a rotatable shafts 16 having agitating fins 17, unraveling and making the crystal material supplied from the inlet 12 flow upwardly.

In order to refine the crude crystal including impurities by using the melted liquid containing the refined crystal component, the crude crystal is supplied to the refiner 11 from the inlet 12 and agitated by the agitator 18 to flow toward the top of the refiner 11. The agitator 18 unravels the crude crystal to prevent the crude crystal from flowing upwardly in lump or attaching to the agitating fins 17. After the crystal arrives at the top of -2the refiner 11, a necessary volume of the crystal is melted to as a circulating melted liquid, which flows downwardly in the refiner 11 by its gravity. The upwardly flowing crude crystal is washed to the desired purity level by the counterflow-contact with the melted liquid and taken out from the outlet 15 at the top of the refiner 11. The impurities included in the crude crystal fall in the refiner 11 and are removed from an exhaust port 20 after separated by a filter 19.

However, since this type of refiner is furnished with the melting heater 14 at the upper part of the refiner, the melting heater 14 is subjected to strong pressure from the upcoming crystal. In addition, the pressure produces counter-pressure, which is applied to the agitator 18.

Consequently, the melting heater 14 and the agitator 18 can be damaged.

One of solutions for this problem is to reduce the throughput of the crystal. However, such solution reduces the production capacity. Another solution is to use a small melting heater to reduce the pressure. However, it reduces the area for the heat transfer and if the same amount of heat is supplied by the small melting heater, the temperature of the melted liquid can be so high that the melting liquid deteriorate.

Moreover, this type of refiner brings about fluctuations in the amount of the upcoming crystal. That is, in this apparatus shwon in Fig. 3, the temperature and the volume of the melted liquid are controlled by adjusting temperature of the melting heater. Namely, the control of the temperature and amount of the melted liquid is made indirectly. It is very difficult to operate this conventional apparatus under appropriate conditions.

Consequently, the operation condition is varied, which in turn affects the heat transfer coefficient, and makes the -3 amount of heat supplied by the melting heater variable and unstable, thereby to cause deterioration of the crystal by heat and reduction of the refining capacity.

Accordingly, it is an object of the present invention to provide an apparatus and a method of refining a crystal, which is able to produce a high quality crystal stably and efficiently by direct control of the temperature and amount of a melted liquid.

DISCLOSURE OF THE INVENTION According to the present invention, there is provided an apparatus for refining a crystal material, which comprises a cylindrical refiner extending vertically, an inlet provided at a lower part of the refiner for supply of the crystal material, an outlet provided at an upper part of the refiner for take-out of a refined crystal, an agitator provided in the refiner and agitating the crystal material, wherein the crystal material is refined by counterflow-contact between a down-flowing melted liquid of a refined crystal component and the up-flowing crystal material.

A device is provided at the upper part of the refiner for supplying the melted liquid to the refiner from outside of the refiner.

The melted liquid of the refined crystal component is supplied to the refiner from the outside at the top of the refiner and flows downwardly so that the upflowing crystal material is refined by the counterflowcontact with down-flowing melted liquid in the refiner.

The agitator does not only agitate but also make the crystal material flow up. The agitator may have a plurality of agitating fins provided at a vertically extending rotatable shaft. The agitator may have a plurality of rotatable shafts, each shaft having the 4agitating fins. At least one of the rotatable shafts may rotate in an opposite direction to a direction of the other rotatable shafts. If the rotation planes of the agitating fins of shafts partly overlap each other when viewed in an axial direction of the shafts, agitating efficiency is increased.

Also, it is preferable that the inlet is connected to a device for pushing the crystal material in the refiner so that the capacity for supplying the crystal material is increased. In addition, the apparatus comprises a filter at the lower part of thereof and an impurity outlet under the filter.

BRIEF DESCRIPTION OF THE DRAWINGS Fig. 1 is a vertical section of a refining apparatus according to an embodiment of the present invention.

Fig. 2 is a section taken along line II-II in Fig.

1.

Fig. 3 is a vertical section of a conventional refining apparatus.

BEST MODE FOR CARRYING OUT THE INVENTION Embodiments of the present invention will now be described with reference to Figs. 1 and 2.

A cylindrical refiner 1 extends vertically and is provided with an agitator 2 therein. The agitator 2 comprises two rotatable shafts 2A extending vertically and each having a plurality of agitating fins 2B. The rotatable shafts 2A may rotate in the same direction or in opposite directions to each other. In either case, it is preferable that the agitating fins 2B have inclination with respect to the horizontal plane so that they create an upflow of a crude crystal inside the refiner 1 during the rotation of the rotatable shafts 2A. As shown in Fig. 2, the plane of rotation of the agitating fins 2B provided on the two rotatable shafts 2A partly overlap each other when viewed from the top. The overlapped area of rotation planes increases the agitating capability. It is preferable that the inside wall of the refiner 1 has a similar shape as the circle of the rotation plane.

The refiner 1 is provided with an inlet 3 at a lower part thereof to supply a crystal material. It is preferable that the inlet 3 is furnished with a means for supplying the crystal material to the inside of the refiner 1 such as a screw conveyer (not shown).

The refiner 1 is also provided at an upper part thereof with an outlet 4 to take out the refined crystal and a means 5 for supplying a melted liquid containing the refined crystal component from the outside of the refiner 1.

The melted liquid supplying means 5 is, in this embodiment, a conduit for supplying a predetermined amount of the melted liquid having an accurately known temperature.

The refiner 1 is provided with a filter 6 at a lower part thereof and an impurity outlet 7 at the bottom thereof.

A crude crystal or crystal-mixed slurry is supplied through the inlet 3 into the refiner 1. The supplied crystal material is agitated by the agitator 2 and carried to the top of the refiner 1. The melted liquid containing the refined crystal component is supplied from the outside at the top of the refiner by the supplying means 5. The optimum amount of the melted liquid, whose temperature is known exactly, is supplied for operation of the refiner 1. A part of the melted liquid moves downwardly into counterflow-contact with the upcoming crystal material to clean the crystal material. Also, the impurities inside the crystal are sweated out by the -6increase of the temperature, thus refining the crystal.

Consequently, the crystal material turns to a crystal having a high purity level when it arrives at the top of the refiner and a part thereof is taken out from the outlet 4 as a product.

The impurities of low melting points included in the crude crystal fall in the refiner and filtered by the filter 6 and exhausted from the impurity outlet 7.

The present invention is not limited to the above illustrated embodiment. Instead of the conduit shown in figures, the melted liquid supplying means may be a plate having a plurality of holes capable of splashing the melted liquid uniformly little by little. The refiner may not be cylindrical but may have any sectional shape. Also, the refiner may stand slightly inclined rather than upright.

(Example) 1260 kg/hour of paradichlorobenzene having a purity rate of 99.99% or more was obtained by supplying 1514 kg/hour of a slurry mixture of 92.3 of paradichlorobenzene, 6.6 of orthodichlorobenzene, and 1.1 of metadichlorobenzene to the refiner 1 shown in Fig.

2, which has two cylinders each having an internal diameter of 508 mm and a height of 2600 mm. By contrast, the refiner disclosed in Japanese Patent Application Kokoku number 47-40621, which has the same size as that of the refiner according to the present invention, produced 800 kg/hour in maximum.

INDUSTRIAL APPLICABILITY As described above, the refiner according to the present invention is provided with no melting heater at an upper part of the refiner in contrast to the conventional refiner so that not only the melting heater is not damaged by the pressure from the upcoming crystal but also the 7 agitator is not damaged by the counter pressure against the pressure.

In addition, since only an appropriate amount of the melted liquid, of which the conditions, such as the temperature thereof, are accurately known, is supplied from the outside, the operating conditions are properly controlled. Consequently, the high quality product free from denature caused by heat is stably obtained with high efficiency.

Claims

8- CLAIMS 1. An apparatus for refining a crystal material by counterflow-contact between a down-flowing melted liquid containing a refined crystal component and an up-flowing crystal material, said apparatus having a cylindrical refiner extending vertically, an inlet provided at a lower part of said refiner for supply of said crystal material, an outlet provided at an upper part of said refiner for take-out of a refined crystal, and an agitator provided in said refiner and agitating said crystal material, charaterized in that said apparatus has, at said upper part of said refiner, means for supplying said melted liquid containing said refined crystal component to said refiner from outside of said refiner. 2. The apparatus for refining a crystal material according to claim 1, wherein said agitator makes said crystal material flow up. 3. The apparatus for refining a crystal material according to claim 1 or 2, wherein said agitator comprises at least one vertically extending rotatable shaft having at least one agitating fin. 4. The apparatus for refining a crystal material according to claim 3, wherein said agitator comprises a plurality of rotatable shafts, each having said at least one agitating fin. The apparatus for refining a crystal material according to claim 4, wherein at least one of said rotatable shafts rotates in an opposite direction with respect to a direction of the other rotatable shafts. 6. The apparatus for refining a crystal material according to claim 4 or 5, wherein rotation planes of said rotatable agitating fins provided at said plurality of said -9 rotatable shafts partly overlap each other when viewed in an axial direction of said rotatable shafts. 7. The apparatus for refining a crystal material according to claim 1, wherein said inlet is connected to means for pushing said crystal material in said refiner. 8. The apparatus for refining a crystal material according to claim 1, which further comprises a filter at said lower part thereof and an impurity outlet under said filter.
9. A method of refining a crystal material by counterflow-contact between a down-flowing melted liquid containing a refined crystal component and an up-flowing crystal material in a cylindrical refiner extending vertically and having an inlet at a lower part thereof for supply of said crystal material, an outlet at an upper part thereof for take-out of a refined crystal, and an agitator therein for agitating said crystal material, charaterized in that said melted liquid containing said refined crystal component is supplied at an upper part of said refiner from outside to said refiner to flow downwardly.