JP3267318B2 - Crystal slurry centrifugation method and apparatus - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a centrifugal separation method and a centrifugal separation method for solid-liquid separation of a crystal slurry obtained by crystallizing a target substance from a liquid containing a plurality of components and its crystals and a mother liquor. In the process, a part of the crystal is melted, and the adhered mother liquor and impurities contained in the crystal are efficiently separated to obtain a high-purity crystal.

[0002]

2. Description of the Related Art In order to crystallize a target substance from a liquid containing a plurality of organic substances and recover the target substance, the crystal slurry is supplied to a filter or a centrifugal separator, and the crystals are separated into a mother liquor. And reducing the amount of the adhered mother liquor as much as possible, or by applying a cleaning liquid to improve the cleaning efficiency and improve the purity.

[0003]

However, in this case,
The mother liquor attached to the surface is removed using centrifugal force or differential pressure, and the attached mother liquor is replaced and washed with a washing liquid.
Its dewatering and cleaning effects are limited. In order to exceed this limit, there are measures such as enlarging the crystal, increasing the dewatering rate under high pressure or centrifugal force, and using a larger amount of a cleaning solution, but this leads to an increase in equipment costs and running costs.

[0004] Therefore, an object of the present invention is to ensure high-purity crystals while suppressing an increase in running cost as much as possible by other means without using such means.

[0005]

Means for Solving the Problems The object of the present invention is to provide a method for centrifuging a slurry obtained by crystallizing a target substance from a liquid containing a plurality of components of an organic substance, by heating a product cake produced by the centrifugation to remove crystals. Crystal slurry to a temperature higher than its melting point
Centrifugation method, wherein the heating is performed with a heated gas
In both cases, pass the heated gas through the formed cake part.
And a centrifugal separation method for crystal slurry characterized by the following .

In this case, the heating gas may be a vapor of the liquid of the slurry or a mixed gas obtained by mixing an inert gas with the vapor.

[0007] Further, as a first aspect, as a first aspect, a supply pipe for heating gas is provided facing the rotating basket, and a gas discharge pipe is provided facing the outside of the basket. The exhaust gas is connected to the supply pipe to form a circulation pipe, and gas heating means is provided in the middle of the circulation pipe, or as a second mode, a supply pipe of the heating gas facing the rotating basket. A gas discharge pipe facing the inside of the basket, and connecting the exhaust gas from the discharge pipe to the supply pipe to form a circulation pipe. This problem can be solved by providing a separator and providing gas heating means between the gas-liquid separator and the supply port of the supply pipe.

[0008]

According to the present invention, the following effects can be obtained by heating the formed cake to a temperature higher than the melting point of the crystal. (1) With the heating, the viscosity of the adhered mother liquor decreases, and the dewatering property increases. (2) When the surface of the crystal itself comes into contact with the heated gas, a part of it melts and is removed together with the residual adherent mother liquor. Separation efficiency increases. (3) The melting of the crystal surface also melts and removes impurities contained in and near the crystal surface, thereby increasing the purity of the separated crystal. (4) In particular, when the present invention is applied to a eutectic crystallization separation equipment, surprisingly, the eutectic point composition exceeds the It was found that the target material could be recovered.

FIGS. 1 and 2 show an apparatus for centrifuging a crystal slurry after crystallization by the crystallization apparatus used in the present invention.

FIG. 1 shows an example of a horizontal type, in which a basket 2 is co-rotated with a rotating shaft 4 in the housing 1 by an output of a driving motor 3. One end of the basket 2 is opened, and a large number of filtrate permeation holes 2a are formed in the peripheral wall. Further, the lower part of the housing 1 is provided with an annular sealing material 5 on the opening side of the basket 2 and on the side corresponding to the basket 2.
Each is divided into a cake discharge zone Z1 and a filtrate discharge zone Z2, and the cake C 'and the filtrate L are discharged from discharge ports 6a and 7a below the discharge chutes 6 and 7, respectively. The crystal slurry S crystallized by a crystallizer (not shown) is supplied from the slurry supply path 8 into the basket 2.

[0011] Such a centrifuge itself is basically known. In the present invention, the formed cake C is heated so as to be higher than the melting point of the crystals.

In the present invention, a heating gas is used as the heating means. That is, a gas which does not affect the purity and physical properties of the crystal, for example, an inert gas G0 such as nitrogen, is fed into the housing 1 through the feeding pipe 10. On the other hand, the heated gas that passed through cake C and basket 2
The gas is discharged from an appropriate position outside the basket 2, for example, from the middle of the gas-liquid separation chute 7 to the outside of the system via the discharge pipe 11. In this case, the gas G0 to be supplied is heated by the heater 12 in advance.

On the other hand, without introducing gas from outside,
Vapor generated due to heating in the crystal slurry can also be used. Of course, both can be used together.
In the case of using the vapor generated due to the heating, the gas from the discharge pipe 11A passes through the circulation pipe 13 which also functions as a supply pipe, and after being heated by the heater 14, the blower ( (Not shown) or the like.

FIG. 2 shows a vertical example in which a gas-liquid separator 15 is provided outside the housing 1. Since this part is basically the same as the example of FIG. 1, the description is omitted.

In the above example, the heating gas is passed through the cake C and the basket 2. However, the same effect can be obtained when the heating is sufficient when the cake C and the basket 2 are simply passed along the surface of the cake C.

In the above example, since the basket 2 is rotating at a high speed, when the inside and outside are partitioned by the sealing material 5, a pressure difference is generated, and the warming gas permeates well. In addition, since the basket 2 is rotating at a high speed, when the circulation pipeline 13 is configured by the backwind effect, natural circulation can be performed without using a blower. If the circulation amount is insufficient, a blower can be used.

Further, as shown in FIG. 3, the heated gas is provided with a divided outlet 16 provided corresponding to the cake C,
It can be sprayed directly. further,
The air volume can be adjusted for each divided zone.

In the present invention, particularly when the present invention is applied to a eutectic crystallization separation equipment, the fact that the eutectic point composition has been considered to be the limit of recovery has been considered. The target can be collected. That is, when the crystal can is operated at the eutectic point P shown in FIG. 4, another eutectic component is precipitated together with the target component. When centrifuged as it is, the cake layer is in a state where the target component and other components are mixed at the same ratio as the eutectic structure, and the recovery cannot be increased. But,
When the melting point of the target component is higher than that of another eutectic component, the other eutectic components are preferentially melted by contact with the heated gas, and the discharged cake layer is rich in the target component. And increase the recovery rate as a result.

In the present invention, the temperature of the heating gas is not lower than the temperature of the crystal slurry and the melting point of the crystal plus 50 ° C.
The temperature is preferably set to 20 ° C. or lower.

[0020]

DESCRIPTION OF THE PREFERRED EMBODIMENTS Embodiments of the present invention will be described to clarify the effects. (Example 1) <PDCB-ODCB system> PDCB (paradichlorobenzene) 20%, ODCB
(Orthodichlorobenzene) 80% of the mixture is cooled,
The cooling was continued even after the temperature reached -20 ° C eutectic temperature, and when the slurry concentration was about 25%, the crystals were separated by the centrifugal separator shown in FIG. As a result, crystals: 20.5% of PDCB, 79.5% of ODCB Mother liquor: 19.7% of PDCB, 80.3% of ODCB, and both showed almost eutectic compositions. When performing the same operation as above and separating, 0 ° C. N ₂ gas is applied for 1 _second for 20 seconds.
After passing at a rate of m ³ / m ² Hr, the separated cake and the mother liquor were analyzed. As a result, crystals: 2% PDCB, 98% ODCB Mother liquor: 15% PDCB, 85% ODCB Could be recovered.

(Example 2) Paraxylene 60% and orthoxylene 40%
After cooling and crystallizing at 11.8 ° C. and without heating the circulating gas, the mixture was continuously separated for 10 minutes by the centrifugal separator shown in FIG. 2 at substantially the same temperature as the slurry temperature.
It was as follows. Crystal cake composition: 97.5% para-xylene, 2.5% ortho-xylene Separated mother liquor: 50% para-xylene, 50% ortho-xylene From this composition, it is judged that the attached mother liquor was 5%. When the same operation is performed and the separation is performed after the separation, the circulating gas temperature is set to 20 ° C., the operation is continuously performed for about 10 minutes, and the discharged cake and the mother liquor are analyzed. At this time, the crystal concentration before the separation is 25%. there were. Discharge cake composition: 99.2% of para-xylene, 0.8% of ortho-xylene Separated mother liquor: 53.1% of para-xylene, 46.9% of ortho-xylene It was found that the purity was significantly improved.

[0022]

As described above, according to the present invention, high-purity crystals can be reliably obtained while suppressing an increase in running cost as much as possible.

[Brief description of the drawings]

FIG. 1 is a schematic diagram showing a first embodiment of the present invention.

FIG. 2 is a schematic diagram showing a second mode.

FIG. 3 is a sectional view of a main part of another example.

FIG. 4 is an explanatory diagram of a eutectic.

Claims (4)

(57) [Claims] 1. A method for centrifuging a slurry obtained by crystallizing a target substance from a liquid containing a plurality of components of an organic substance, wherein a product cake accompanying the centrifugation is heated to bring a crystal to a temperature higher than its melting point. Centrifugation method of slurry
I, along with performing the warming heating gas, the heating gas raw
A method for centrifuging a crystal slurry, wherein the crystal slurry is passed through a part of the formed cake . 2. The method for centrifuging a crystal slurry according to claim 1, wherein the heating gas is a vapor of the liquid of the slurry or a mixed gas obtained by mixing an inert gas with the vapor. 3. A device for centrifuging a slurry obtained by crystallizing a target substance from a liquid containing a plurality of components of an organic substance, wherein a heating gas supply pipe is provided facing a rotating basket, and a heating gas supply pipe is provided facing the outside of the basket. A crystal characterized by providing a gas exhaust line, connecting exhaust gas from the exhaust line to the supply line to form a circulation line, and providing gas heating means in the middle of the circulation line. Centrifuge for slurry. 4. An apparatus for centrifuging a slurry obtained by crystallizing a target substance from a liquid containing a plurality of components of an organic substance, wherein a heating gas supply pipe is provided facing a rotating basket, and a heating gas supply pipe is provided facing the rotating basket. A gas discharge line is provided, a discharge line from the discharge line is connected to the supply line to form a circulation line, and a gas-liquid separator is provided in the middle of the circulation line. Wherein a gas heating means is provided between the supply pipe and a supply port of the supply pipe.