JPS594401A - Purification device of crystal - Google Patents

Abstract

PURPOSE:To purify with high purity and high yield an intended crystal component from crude raw material crystals by providing a purification stage and a recovering stage in a refining column, removing the crystals purified in the respective divided chambers once to the outside of the column, and cooling the same forcibly then feeding the crystal into the next chambers. CONSTITUTION:A purifying stage which is the stage above a chamber 3 having a supply port 10 for raw material and a recovering stage which is the stage below the chamber 3 are provided to a purification column 1. The crystals discharged through the crystal discharge ports 8 of the respective chambers 3 in the purification stage are cooled forcibly with a cooler 9 and are then supplied into the next purification chambers, and the liquid discharged through liquid discharge ports 5 is supplied from the corresponding chambers to the previous purification chambers. The liquid discharged from the first purification chamber to be supplied with a crude raw material crystal through a supply port 10 for raw material is cooled with a cooler 9' and is thus crystallized, whereafter the crystal is supplied into the lower recovering stage. In the recovering stage as well, the discharged crystal is supplied to the next crystal supply chamber for higher purity similarly, and the discharged liquid is supplied to the previous crystal supply chamber for lower purity.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a crystal purification apparatus that continuously processes a crystalline substance containing impurities using a purified melt of the crystal component.

Conventionally, there are various crystal purification apparatuses, but an example of an apparatus for purifying a target crystal component using melting 11 is the one disclosed in Japanese Patent Publication No. 47-40621. The device disclosed in the publication has a means in the lower part for feeding the substance to be purified containing impurities into the column, and a means for melting the purified crystals in the upper part and returning a part of it to the column as a washing liquid for impure crystals. 4.7 Into an upright VIV tower with a means for taking out the purified material to the outside, l+li4 rectangular blades are installed in the form of a single spiral staircase to feed the crushed crystals into the tower. It has both the function of loosening the crystals and the function of pushing the crystals upwards (+iif). Two or more rotating stirrers are provided, and the crystalline substance is purified while being raised inside the column so as not to solidify the crystals.

When using a crystal purification apparatus with such a configuration to purify crude crystals containing impurities using a melt of the target crystal component,
Raw material crude crystals are introduced from the bottom of the tower, and a shield installed inside the tower,
It is lifted up towards the top of the tower by stirring. The required amount of crystals that reach the top of the column are melted and become a reflux liquid, which flows down the column by gravity. The remaining crystals are extracted and made into a finished product.

The present inventors endeavored to analyze the mechanism of this crystal refining, and found that the crystals lifting up in the column have a washing effect on the surface of the crystals due to continuous countercurrent contact with the highly pure melt flowing down. Impurities encapsulated in the solid or impurities dissolved in the solid are caused by mass exchange (sweating effect) during the sufficiently long stay of the crystal in the column, and by recrystallization that occurs as the descending reflux liquid loses heat as it descends. It turns out that these changes are occurring at the same time.

The main effect among these effects is the cleaning effect, but it is clear from the graph in FIG. 1 that other effects occur. FIG. 1 is a graph showing the relationship between the amount of washing solution and the impurity content of the crystals after continuously washing the crude crystals with a sufficiently large amount of pure solution. It is understood that there are limits to the purity that can be achieved. However, the purity of the crystals treated with the purification apparatus described in Japanese Patent Publication No. 47-40621 corresponds to the rightmost point of the dotted line in FIG. 1, and exceeds the purity obtained in the washing experiment. This is because in addition to the cleaning action, it also has the functions of sweating and recrystallization. If the eutectic crude crystals are kept near their melting point for 1 hour and then washed with a pure liquid, the purity approximately shown by the dotted line is reached, which suggests that the perspiration effect is large. When the crude crystals are a solid solution, sufficient purity cannot be achieved by washing and perspiration alone. However, if the target crystal component forms a solid solution with impurities, it may be necessary to further strengthen the recrystallization effect.
In the above-mentioned apparatus, we cannot expect much from the recrystallization effect from the standpoint of heat balance.

In researching how to enhance the recrystallization effect in the crystal purification apparatus, the present inventors focused on a precision separation method using a distillation method that has been practiced for a long time. In the case of a distillation method, a method of increasing the reflux amount is adopted as a means of achieving precision separation, but the reflux amount cannot be increased much in the crystal purification column because of the essential structural difference from the distillation column.

The present inventors have conducted research to resolve this difficulty and purify the target crystal component from raw material crude crystals with high purity and high yield.As a result, the purification tower was divided into multiple stages, each consisting of a plurality of chambers. The present invention has been developed in which a recovery stage is provided, and the crystals purified in each divided chamber are once extracted outside the column and the forcibly cooled crystals are sent to the next chamber. Here, the purification stage is a stage for increasing the purity of the supplied raw material, and the recovery stage is a stage for raising the purity of the supplied raw material to that of the raw material and recovering it.

The apparatus of the present invention will be explained in detail below with reference to the accompanying drawings.

FIG. 2 is a cross-sectional view of one example of the device of the present invention, and FIG. 6 is a longitudinal cross-sectional view thereof.

The apparatus of the present invention has a purification stage and a recovery stage, each of which has a cross section divided by two or more circles (hereinafter referred to as chambers). The purification stage is a stage above the chamber having the raw material supply port 10, and the recovery stage is a stage below it.

Each chamber 3 of the purification stage and recovery stage has a heating means inside, a solid-liquid separation plate 4 at the bottom, a liquid extraction port 5 below the solid-liquid separation plate 4, and a crystal supply port to be purified above the solid-liquid separation plate 4. 6, and a crystal extraction port 8 is provided at the top. In the refining stage, the crystals taken out from the crystal extraction port 8 of each chamber 3 are placed in a cooler 9.
After forced cooling, the liquid is supplied to the next purification chamber, and the liquid extracted from the liquid extraction port 5 is supplied to the purification chamber before this chamber. Further, the liquid extracted from the first refining chamber to which the raw material crude crystals are supplied from the raw material supply port 10 (corresponding to 6) is cooled and crystallized by the cooler 9' and then sent to the lower recovery stage. Similarly to the purification stage i, the recovery stage is configured so that the extracted crystals are supplied to the next crystal supply chamber of higher purity, and the extracted liquid is supplied to the previous crystal supply chamber of lower purity.

The agitator 12 provided inside the purification column 1 has rotating shafts 128, 128' at the center of each day in FIG.
, 12B' are arranged and attached in a spiral line. This set of stirrers 12, 12' are mutually arranged in such a way that the blades 12B are located between the blades 12B'h of the other stirrers, and the tips of the blades are as close as possible to the axis of rotation of the other stirrers. installed to do so. Further, the heating means provided in each chamber is, for example, a heating medium. Alternatively, it may be provided as an independent device T that electrically heats, or the stirrer 12 may have a heating function. When a stirrer is provided with a heating function, in addition to using the entire stirrer as a heating means, only the rotating shaft or a portion of the rotating shaft and the blades, for example, the blades located at the top of each chamber, are provided with the heating function. The following modes can be taken.

Crystal purification using the apparatus of the present invention will be explained with reference to FIG.

First of all, the raw material crude crystals! The raw material is cooled to constant humidity and supplied to the first purification chamber through the raw material supply port 10. In continuous operation, the effluent from the next yI production chamber is also supplied to the first purification chamber. At least the upper end of each chamber is maintained at a temperature of one degree or slightly higher than the melting point temperature of the target crystal component.

The crystals extracted from the outlet after crystallization in the first refining chamber are placed in the cooler 9.
It is forcibly cooled and supplied to the next refining room.

In this way, the extracted crystals from each purification chamber are sequentially sent to the next purification chamber, and their purity is successively improved. The desired purified crystals are obtained from the crystal extraction port 11 of the final purification chamber. On the other hand, the liquid extracted from each purification chamber after the second purification chamber is sent as it is, or in liquid form after heat removal, or after being cooled as necessary to partially or completely crystallize it, to any suitable chamber before it. Supplied. At this time, the chamber to which the extracted liquid is supplied is a chamber in which the purity of the crude crystals supplied to the chamber is the same as or lower than the purity of the extracted liquid. The crude crystals and extracted liquid can be supplied to each refining chamber by cooling them separately and supplying them from one supply port as shown in the figure, or by cooling the crystals and extracted liquid together in one cooler and supplying them to the next nine chambers. It is also possible to take the form of supplying it to In some cases, the extracted liquid may not be cooled,
Ru.

By repeating this process in multiple stages, the crystals and extracted liquid are extracted from each of the N-made stages provided in multiple stages, and the crystals are returned to the next refining stage, and the extracted liquid is returned to the previous refining stage. Any amount of recrystallization can be performed.

The number of refining stages required is determined by the properties of the raw material crude crystals and the desired purity.

In addition, the liquid extracted from the first refining chamber to which raw material crude crystals are supplied is supplied to the recovery stage, and the crystals are purified by the same mechanism as in the refining stage, so that they are equivalent to the raw material crude crystals. The crystals with a purity higher than that are supplied to the purification stage,
Impurities are taken out of the column from the liquid extraction port 13 of the final recovery chamber.

According to the present invention, it is possible to perform not only the cleaning action and perspiration action but also the recrystallization action in any desired amount. Therefore, not only when the impurities present in the raw material crude crystal are components that form a eutectic system with the target crystal component, but also when they are components that form solid solution threads that are difficult to purify, it is necessary to purify them to extremely high purity. It's because it's so beautiful! rate is significantly improved.

Further, the purification according to the present invention has the advantage that the separation of substances is carried out at a melting point much lower than the boiling point of the substance, so that the product can be processed with less thermal destruction. Furthermore, a high heat source used for crystal purification according to the present invention,
When the target crystal component has a melting point of about 200"C or less as a low heat source, there is an advantage that a low-cost material such as waste heat from a factory can be used.

The apparatus of the present invention can be applied to and purify almost any crystalline substance. Some examples of such substances include naphthalene, paraxylene, and dichlorobenzene.

[Brief explanation of drawings]

Fig. 1 is a graph showing the relationship between the amount of washing liquid and purity when crude crystals are washed with a pure liquid, Fig. 2 is a cross-sectional view of an embodiment of the apparatus according to the present invention, and Fig. 6 is a graph showing the relationship between the purity and the amount of washing liquid when crude crystals are washed with a pure liquid. FIG. DESCRIPTION OF SYMBOLS 1... Purification tower, 2... Partition plate, 4... Solid-liquid separation plate (perforated plate), 5... Liquid, extraction port, 6... Crystal to be purified supply port, 8... Crystal extraction port, 9...Cooler, 1o.
...Raw material supply port, 11...S product outlet, 12...
N, stirrer, 13...liquid extraction port. Above, the size 1 flash figure 2 "A L, 4

Claims (1)

[Claims] ('') The tower has a shape in which circles with lateral FOr planes of 211d or more are partially overlapped, and has a stirrer in the center of each of the above days, with 213 pieces arranged in a spiral line on the surface of the rotating shaft inside. , Cb) Divided into multiple stages, each partitioned palm part has a heating means inside, a solid-liquid separation plate at the bottom, a liquid extraction port below the separation plate, and a crude crystal supply port above the separation plate, and the main (C) A purification system configured so that the liquid extracted from each chamber is supplied to the chamber before the chamber, and the crystals extracted from each chamber are supplied to the next chamber. A crystal refining device characterized by having a stage and a recovery stage.