JPH0659363B2 - Pressure crystallization method - Google Patents

Description

TECHNICAL FIELD The present invention relates to a pressure crystallization method for rapidly extracting a high-purity component crystallized by a pressure crystallization operation and without causing wear of an apparatus.

[Prior Art] In the pressure crystallization method, as shown in FIG. 2, a raw material (fluid phase mixture) composed of a liquid crystal or a solid-liquid mixture composed of a plurality of components is introduced into a high-pressure container (injection step), This is a method of accelerating crystallization of a specific component by applying a high pressure to the raw material in a state where the liquid phase discharge pipe is closed (pressurizing step). can get. Next, after closing the drainage pipe and applying pressure to the solid-liquid coexistence state, the liquid component is discharged out of the system through the filter (separation step), and the remaining solid phase is melted at the surface layer if necessary. When the solid-liquid is separated while pressing (pressing / perspiration process), a high-purity specific component can be obtained. The solidified product of the specific component thus obtained is taken out by opening the high-pressure container and operating the pusher or chute, and then closing the high-pressure container again to start the next operation (extracting step).

[Problems to be Solved by the Invention] When taking out a specific component in such a pressure crystallization method, it is necessary to open and close the container and operate a pusher and the like each time, and it takes a lot of time for this operation. Expenditure (may take more than 1 minute in a few minute cycle). Also, in long-term operation, opening and closing of the container is repeated tens of thousands of times, wear of the packing accompanying opening and closing causes misalignment of the axial center of the lower lid and the container, and due to failure of these devices Unable to operate stably. Furthermore, there is a problem that the liquid with a lot of impurities adhering to the back surface of the filter drops on the solid substance of the specific component and contaminates the specific component when the container is opened.When the container is opened, the solid substance of the specific component comes into contact with air. And causes problems such as reaction with air and moisture absorption. Another problem is that if the solid of the specific component is volatile, the surrounding work environment is deteriorated.

The present invention has been made in view of these circumstances, and an object of the present invention is to provide a pressure crystallization method capable of solving all of the above problems at once.

[Means for Solving the Problems] In the method of the present invention which has achieved the above object, however, pressure crystallization is performed in which a liquid phase mixture composed of two or more components is placed under pressure to generate and increase crystals of a specific component. In the method, when the mother liquor pressure that is separated and discharged from the generated specific component crystals reaches a predetermined pressure, the separation of the mother liquor is stopped, and the pressure applied to the specific component crystals remaining in the high-pressure container is reduced, It has a gist in that a part of the crystal is melted and a specific component is made into a slurry and collected outside the high-pressure container.

[Operation and Examples] The root cause of the above problems is that the container is frequently opened and closed because it is necessary to take out the specific component in the form of a solid.
These problems can be solved all at once if the container can be taken out without opening. That is, after separating the solid of the specific component obtained by the pressure crystallization operation from the liquid phase containing a large amount of impurities, for example, if the solid is heated and melted into a liquid state, the liquid is discharged from the discharge pipe without opening the container. The specific component can be recovered. However, when recovering the entire solid content of a specific component in a container, it takes a considerable amount of time for heating and melting, and it is difficult to separate it from the liquid phase containing a large amount of impurities inside the container, especially around the filter. However, impurities are mixed in the melt of the specific component, and the purity is lowered. Further, if the device is heated for melting, it is necessary to recool before the start of the next cycle, and there are many losses in terms of time and energy.

Therefore, the present inventors further conducted research on a pressure crystallization method capable of rapidly extracting a high-purity specific component from the container without opening the container, and completed the pressure crystallization method shown in the above configuration. Came to.

That is, graphs of changes in pressure with time and changes in temperature-pressure in the adiabatic pressure crystallization operation are shown in FIGS. 3 and 4. In the figure, A is the completion point of the injection process, and AB
Between the pressurizing process, B-C separating process, C-D pressing
Almost compatible with the sweating process. In FIG. 4, a is a solid-liquid equilibrium line of a specific component (pure substance), b is a solid-liquid equilibrium line of raw material composition,
M represents the melting point of the specific component (pure substance) under atmospheric pressure. Here, in FIG. 4, the purity of the product increases as it approaches the solid-liquid equilibrium line a of the pure substance, and the operating conditions are set so that the point D is as close to the point M as possible.

However, as can be understood from the temperature-pressure change curve of FIG. 4, the curve is already sufficiently close to the solid-liquid equilibrium line a of the pure substance at the point C even if it does not reach the point D. Is taken out, a specific component having sufficiently high purity can be obtained. That is, the reduced pressure between C and D has the effect of causing the surface of the solid substance of the high-purity specific component to sweat and removing the surface layer of relatively low purity to further enhance the purity. It is a little high because it has a very high purity.

Therefore, in the present invention, in order to recover the crystal of the specific component at the point C, the separation / discharge of the liquid phase containing impurities is stopped at the point C. As a stopping method, when the pressure of the drainage line reaches the pressure at point C, for example, as shown in FIG.
Although it is possible to close the valve V _{6 of the above} , it is more preferable to apply a back pressure corresponding to the pressure at the point C to the back fluid line and keep the pressure of the drainage line at this pressure for a while. To be done. As a result, the pressure of the mother liquor remaining in the large-sized high-pressure container becomes the same, and a uniform pressure state can be obtained.

Then, as shown in Fig. 1, crystals of the specific component (solid phase) in the container
A pipe line (solid-phase outflow pipe) 7 communicating with is opened to release the pressure of the solid-phase portion to atmospheric pressure all at once. However, at this time, the specific component crystal at the inlet of the solid phase outflow pipe 7 is exposed to atmospheric pressure, and the specific component crystal around the inlet is C in FIG.
Melting corresponding to the temperature drop between −D occurs, and a slurry in which the melt and the solid phase are mixed is generated.

The generated slurry flows into the solid-phase outflow pipe 7 and the high-pressure container 1
Since it flows out to the outside, a high-purity specific component that is the target substance can be obtained by collecting this. While the solid phase outflow pipe 7 is open, a sufficient surface pressure is applied to the crystal of the specific component by the piston 4 so that the pressure inside the container does not decrease.
As a result, the crystals of the specific component are sequentially melted from the side close to the solid-phase outflow pipe 7, gradually descend as the piston 4 descends, and form a slurry and flow out from the solid-phase outflow pipe 7. Thus, the crystals of the specific component can be promptly taken out without opening the container.

In the above pressure crystallization method, the pressure at the point C, that is, the predetermined pressure at which the liquid phase separation is stopped, includes the type of the specific component, the target product purity, the raw material temperature, the pressure at the point B, that is, the maximum pressurizing point, the temperature, and the like. It is decided in consideration.

However, it is desirable that the liquid phase fraction is at least 0.05 or more when the pressure is reduced from point C to point D. The higher the liquid phase fraction, the smoother the initial discharge, and the smaller the piston pressure required for the specific component crystal extrusion. I'm done.

Further, while the crystals of the specific component are slurried and extruded, a liquid phase having a high impurity concentration separated by the pressure up to the point C exists in the filter outer peripheral gap in the container. However, it will not be mixed into the specific slurry. This is because, during the extrusion of the specific component, the surface pressure of the point C or higher is applied to the crystal of the specific component by the piston, and the crystal is maintained at the high pressure of the solid phase inside the filter.

The diameter of the solid-phase outflow pipe, which is also a means for reducing the pressure applied to the crystals of the specific component, is not particularly limited, but it does not necessarily have to be so large, and an inner diameter of several mm can be treated. This is because the presence of the liquid phase (melt) makes the crystal grain boundaries slippery, and once they start to slide, the temperature rises due to the friction between the crystals and the liquid phase increases, making it more slippery. As a result, the characteristic component can be extruded even if the diameter of the solid-phase outflow pipe is small. It is also an effective means to slightly heat the vicinity of the solid phase outlet to give a trigger for extrusion.

[Effects of the Invention] The present invention is configured as described above, and the effects summarized below can be obtained.

(1) Crystals of a specific component can be slurried and collected from a high-pressure container under a high pressure without flowing in an impurity-containing liquid phase separated from a solid phase. That is, the high-purity specific component can be taken out without opening and closing the high-pressure container, and the wear and failure of the device due to opening and closing can be prevented.

(2) It is not necessary to open and close the container, and the recovery of the specific component can be completed in a short time.

(3) The pressure crystallization cycle can also shorten the squeezing and sweating steps, improving the productivity of the device.

(4) Since the container is not opened, dripping of the back surface of the filter does not occur, and if the slurry-like specific component is directly introduced into the container, inconveniences such as contact with air and emission of volatiles can be eliminated.

(5) The container moving mechanism that was required for opening and closing the container is no longer required, and the height of the entire device can be significantly reduced.

[Brief description of drawings]

FIG. 1 is a schematic explanatory view showing an embodiment of the present invention, FIG. 2 is a flow explanatory view showing a pressure crystallization step, FIG. 3 is a graph showing a change in pressure with time in a pressure crystallization operation, and FIG. It is a graph which shows temperature-pressure change in pressure crystallization operation. 1 ...... pressure vessel, 3 ...... filter 4 ...... piston, 5 ...... lower cover 6 ...... drain line, 7 ...... solid phase outlet pipe V _6, V _{7 ......} valve

Claims (1)

[Claims] 1. A mother liquor pressure which is separated and discharged from the generated crystals of a specific component in a pressure crystallization method in which crystals of the specific component are generated and increased by placing a fluid phase mixture composed of two or more components under pressure. Stops the separation of the mother liquor when reaches a predetermined pressure, lowers the pressure applied to the specific component crystals remaining in the high-pressure container, melts a part of the crystals, and makes the specific component into a slurry to a high pressure. A pressure crystallization method characterized by recovering to the outside of a container.