JPS63218205A - Pressure crystallization method - Google Patents

Abstract

PURPOSE:To rapidly discharge a crystallized high-purity component without damaging equipment, by slurrying the crystal of the specified component while preventing the mixing of an impurity-contg. liq. phase separated from a solid phase under high pressure, and recovering the slurry from a high-pressure chamber. CONSTITUTION:When the mother liquor separated and discharged from the crystal of the specified component formed in pressure crystallization is pressurized to a specified pressure, a back pressure corresponding to the pressure is applied to a waste liq. pipeline 6 to keep the pressure of the line 6 at the pressure for some time, and the separation of the mother liquor is stopped. A solid phase outflow pipe 7 communicating with the specified component crystal (solid phase) in the high-pressure vessel 1 is then opened to instantaneously reduce the pressure of the solid phase part to atmospheric pressure, and the pressure acting on the specified component crystal remaining in the high- pressure vessel 1 is decreased. Consequently, a part of the crystal is dissolved, the specified component is slurried, and the formed slurry is discharged to the outside of the high-pressure vessel 1 from the solid phase outflow pipe 7 and recovered.

Description

DETAILED DESCRIPTION OF THE INVENTION [Industrial Application Field] The present invention relates to a pressure crystallization method for quickly extracting high purity components crystallized by a pressure crystallization operation without damaging the apparatus.

[Prior Art] Pressure crystallization is a process in which a raw material (fluid phase mixture) consisting of a liquid phase or a solid-liquid mixture consisting of multiple components is introduced into a high-pressure container as shown in Figure 2. This is a method (pressurization process) in which high pressure is applied to the raw material with the liquid phase discharge pipe closed to promote crystallization of a specific component, and this operation creates a state in which crystals of the specific component and residual liquid are mixed. can get. Next, the drain pipe is unblocked and the liquid component is discharged out of the system via a filter while applying pressure to the solid-liquid coexistence state (separation process), and the remaining solid phase is compressed after melting the surface layer if necessary. By separating the solid and liquid (squeezing and sweating process), a highly pure specific component can be obtained. The specific component solidified product thus obtained is taken out by opening the high-pressure container and operating a button or chute, and then the high-pressure container is closed again and the next operation begins (take-out 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 the pusher each time, and this operation requires a large amount of time. (can take more than a minute in a cycle of several minutes)
In addition, during long-term operation, the container will be opened and closed tens of thousands of times, resulting in wear and tear on the gaskets and misalignment of the axis between the bottom lid and the container. It is not possible to perform stable and stable operations. Furthermore, when the container is opened, the highly impure liquid adhering to the back of the filter drips onto the specific component solids and contaminates the specific components, and when the container is opened, the specific component solids come into contact with the air. This causes problems such as reaction with air and moisture absorption.

Another problem is that if the specific solid component is volatile, it may worsen the surrounding working environment.

The present invention has been made in view of these circumstances, and it is an object of the present invention to provide a pressure crystallization method that can solve the above-mentioned problems all at once.

[Means for Solving the Problems] The method of the present invention that achieves the above object is a pressure crystallization method in which crystals of a specific component are generated and increased by placing a fluid phase mixture consisting of two or more components under pressure. In this method, the separation of the mother liquor is stopped when the pressure of the mother liquor separated and discharged from the generated specific component crystals reaches a predetermined pressure.
The gist of this method is to reduce the pressure applied to the specific component crystals remaining in the high-pressure container, melt some of the crystals, and collect the specific component into a slurry form outside the high-pressure container.

[Operations and Examples] The root cause of the above-mentioned problems is that the container must be opened and closed frequently due to the need to extract specific ingredients in solid form.
If it were possible to take out the container without opening it, these problems would be solved at once. That is, after separating the specific component solid obtained by pressure crystallization from the liquid phase containing many impurities, for example, if the solid is heated and melted to a liquid state, it can be discharged from the discharge pipe etc. without opening the container. Liquid specific components can be recovered. However, when recovering a specific component solid by melting it in its entirety in a container, it takes a considerable amount of time to heat and melt it, and it is difficult to separate it from the liquid phase containing many impurities that remains inside the container, especially around the filter. , impurities will be mixed into the specific component melt, reducing the purity. Furthermore, if the device is heated for melting, it must be cooled again before the start of the next cycle, resulting in a large loss in terms of time and energy.

Therefore, the present inventors conducted further research on a pressure crystallization method that can quickly take out a high purity specific component from a container without opening the container, and completed the pressure crystallization method shown in the above configuration. reached.

That is, when the pressure change over time and the temperature-pressure change in the adiabatic pressure crystallization operation are graphed as shown in Figs. 3 and 4, A-8 in Fig. 0 is the point at which the injection process is completed.
The space between is the pressurizing process, the space between B and C is the separation process, and the space between C and D is the compression process.
It roughly corresponds to the sweating process. Also, a in Figure 4 represents a specific component (
b is the solid-liquid equilibrium line of the pure substance), b is the solid-liquid equilibrium line of the raw material composition, M
indicates the melting point of a 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 pure substances, and the operating conditions are set so as to bring point D as close as possible to point M.

However, as can be understood from the temperature-pressure change curve in Figure 4, the curve is already sufficiently close to the solid-liquid equilibrium line a of the pure substance at point 0 even before reaching point D, and the solid-liquid equilibrium line a of the pure substance at this time By extracting it, it is possible to obtain a specific component with a sufficiently high purity. In other words, when the pressure is reduced between C and D, the surface of the high-purity specific component solid material sweats, and the relatively low-purity surface layer is removed to further increase the purity, but the purity improvement during this period is 0 points. The amount is very small, partly because the purity is quite high.

Therefore, in the present invention, it was decided to stop the separation and discharge of the impurity-containing liquid phase at the 0 point in order to recover the specific component crystals at the 0 point. As a method of stopping, when the pressure in the drain line reaches the zero point pressure, for example, as shown in Fig. 1, the drain line 6 is stopped.
Although it is possible to close valve v6, it is more preferable to apply a back pressure equivalent to the zero point pressure to the drain line and maintain the pressure in the drain line at this pressure for a while. Ru. As a result, the mother liquor pressure remaining in the large high-pressure container becomes the same pressure, and a uniform pressure state can be obtained.

Next, as shown in Figure 1, the specific component crystals (solid phase) in the container
The pipe line (solid phase outflow pipe) 7 communicating with is opened, and the pressure in the solid phase part is released all at once to atmospheric pressure. However, at this time, it is the specific component crystals in the solid phase outflow tube 7 that are exposed to atmospheric pressure, and the specific component crystals around the inlet are exposed to C in FIG.
Melting occurs corresponding to the temperature drop between -D, and a slurry containing a mixture of melt and solid phase is generated.

The generated slurry flows into the solid phase outflow pipe 7 and is transferred to the high pressure vessel 1.
Since it flows out to the outside, if this is collected, a high purity specific component, which is the target substance, can be obtained. Even while the solid phase outflow pipe is open, sufficient surface pressure is applied to the specific component crystals by the piston 4 to prevent the pressure inside the container from decreasing.
As a result, the specific component crystals are sequentially melted from the side closer to the solid phase outflow pipe 7, gradually descend as the piston 4 descends, and flow out from the solid phase outflow pipe 7 in the form of a slurry. In this way, specific component crystals can be quickly taken out without opening the container.

In the above pressure crystallization method, the pressure at the zero point, that is, the predetermined pressure at which liquid phase separation is stopped, depends on the type of specific component, the target product purity, the raw material temperature, the pressure and temperature at point B, or the maximum pressurizing point, etc. Determined by consideration.

However, it is desirable that the liquid phase fraction when the pressure is reduced from 0 point to D point is at least 0.05 or more, and the higher the liquid phase fraction, the smoother the initial discharge, and the piston pressure required to extrude the specific component crystal. can be reduced.

Also, while the specific component crystals are slurried and extruded, a liquid phase with high impurity concentration that is separated by pressure down to zero exists in the gap around the filter periphery in the container. On the contrary, it will not pass through and mix into the specific slurry. This is because, during extrusion of the specific component, surface pressure greater than the pressure at point C is applied to the specific component crystal by the piston, and the solid phase inside the filter is held at a higher pressure.

There is no particular restriction on the diameter of the solid-phase outflow tube, which is also a means of reducing the pressure applied to the specific component crystals, but it does not necessarily have to be so large, and treatment may be possible with a diameter of about 100. This is because grain boundaries become slippery due to the presence of a liquid phase (melt material), and once they begin to slide, the temperature rises due to friction between the crystals, the liquid phase increases, and the grain boundaries become slippery. As a result, specific components can be extruded even if the diameter of the solid phase outflow tube is small.

It is also an effective means to slightly heat the vicinity of the solid phase outlet to trigger extrusion.

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

(1) Specific component crystals can be slurried and recovered from a high-pressure container without introducing an impurity-containing liquid phase separated from a solid phase under high pressure. That is, the high-purity specific component can be taken out without opening and closing the high-pressure container, and it is possible to prevent wear and tear on the device due to opening and closing.

(2) There is no need to open and close the container, and recovery of specific components can be completed in a short time.

(3) The pressure crystallization cycle also improves the productivity of the device by shortening the squeezing and sweating steps.

(4) Since the container is not opened, there is no possibility of liquid dripping on the back of the filter, and if the slurry-like specific component is directly introduced into the container, inconveniences such as contact with air and the dissipation of volatile substances can be eliminated.

(5) The container moving mechanism required to open and close the container is no longer necessary, and the height of the entire device can be significantly reduced.

[Brief explanation of the drawing]

Fig. 1 is a schematic explanatory diagram showing an embodiment of the present invention, Fig. 2 is a flow explanatory diagram showing a pressure crystallization process, Fig. 3 is a graph showing changes in pressure over time in the pressure crystallization operation, and Fig. 4 is It is a graph showing a temperature-pressure change in a pressure crystallization operation. 1...High pressure container 3...Filter 4...Piston 5...Lower lid 6...Drain line
7...Solid phase outflow tube V,,V,...Valve Figure 1 Figure 2

Claims (1)

[Claims] In the pressure crystallization method in which crystals of a specific component are generated and increased by placing a fluid phase mixture consisting of two or more components under pressure, the pressure of the mother liquor separated and discharged from the generated crystals of the specific component reaches a predetermined pressure. At this point, 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 to melt some of the crystals, making the specific component into a slurry and recovering it outside the high-pressure container. A pressure crystallization method characterized by: