JPH02126903A - Pressure crystallization method - Google Patents

Abstract

PURPOSE:To definitely attain the liquid phase-component discharge speed adequate in view of the yield and output of a product by discharging a liquid phase-component while controlling the liquid phase-component discharge speed by a stepless speed change mechanism having variable resistance to fluid. CONSTITUTION:A mixture (e.g., a cresol soln.) composed of >=2 kinds of components contg. a specific component is supplied to a high-pressure vessel and this mixture is pressurized in the above-mentioned vessel to attain a solid- liquid co-existence state. The liquid phase-component is in succession discharged to the outside of the vessel under pressurization and is subjected to a solid-liquid sepn. The residual liquid is squeezed out by compressing and is discharged to the outside of the vessel, by which the solid product of the specific component (e.g.; p-cresol) is formed in the vessel; thereafter, the product is taken out of the vessel. The discharge of the liquid phase-component is executed while the liquid phase-component discharge speed is controlled by the stepless speed change mechanism which consists of a nozzle body 17, a lens-shaped valve seat 19 having a hole 18, a valve stem 20, etc., and has the variable resistance to fluid at this time.

Description

DETAILED DESCRIPTION OF THE INVENTION (Field of Industrial Application) The present invention relates to a pressure crystallization method, and more particularly, to a pressure crystallization method for controlling and adjusting the rate of liquid phase discharge in a solid-liquid separation process. Regarding.

(Conventional technology) Pressure crystallization has great potential for application to raw material systems that are difficult to separate using conventional distillation or cooling crystallization, is easy to obtain high-purity products, and has high Bunto refining technology has been attracting a lot of attention as the chemical industry has become increasingly refined in recent years due to its easy yield and low energy consumption.

An overview of this pressure crystallization method can be found, for example, in Kagaku Kogyo Volume 50 (
(1986), p. 331, "Outline of pressure crystallization method and apparatus". To explain this using Figure 1 (a diagram showing the process flow and the concept of the device), the pressure vessel (1)
A lid body (lower m) (2) is provided below, and a piston (5) is provided to move up and down within the container (1) by the operation of a hydraulic unit (3). (
5) and the lower M(2) form a crystallization chamber (4) within the pressure vessel (1). This crystallization chamber (4) and the drain tank (
6) means the pipe (9) via the pressure reducing mechanism 00 and valve 01).
) are connected. Further, the crystallization chamber (4) and the pre-crystallizer (7) are connected to each other by a piping side via a raw material supply pump (8) and a valve 02).

A filter (not shown) is arranged on the inner surface of the body of the crystallization chamber (4). Further, the pressure reduction mechanism 00 is provided to adjust the liquid phase discharge rate, which will be described later, and uses a small-diameter orifice, that is, a pressure reduction nozzle. This diameter is, for example, 0°10 to 0.45 mmφ, and the diameter is selected depending on the target liquid phase discharge speed. The diameter of 0.10φ is the minimum diameter that can be manufactured.

In this apparatus, the raw material is fed from the raw material tank side to the pre-crystallizer (7), where it is cooled to produce seed crystals for pressure crystallization. This is because when raw materials without seed crystals are subjected to pressure crystallization, the supersaturation pressure is generally relatively high, typically several hundred atmospheres or more, and high pressure is required for initial crystal formation. This is because there is a risk that the slurry containing seed crystals will be supplied, which has the advantage that not only is there no need to worry about such supersaturation pressure, but crystal growth can be expected without nucleation due to pressurization.

Next, the raw material is transferred from the pipe 0 to the crystallization chamber (4) via the valve 02.
). When the crystallization chamber (4) is filled with the raw material, the liquid begins to flow out through the overflow pipe θω having an opening at the tip of the piston.This is detected and the valve 021.0
ω is closed and pressurization by the piston (5) is started. When the raw material liquid is pressurized, crystallization of specific substances in the raw material progresses,
The inside of the crystallization chamber (4) is in a solid-liquid equilibrium state under high pressure. The solid produced at this time is generally a substance of extremely high purity. Note that the temperature inside the crystallization chamber (4) rises due to assimilatory latent heat generated as solidification progresses, but in the pressure crystallization method, cooling is generally not performed to prevent this temperature rise, and heating is performed adiabatically. A pressure method is adopted. The temperature reached after the temperature rise, that is, the temperature at which solid-liquid separation starts, affects the purity and yield of the product, so this is adjusted by the temperature of the supplied liquid, taking into consideration the specific heat, latent heat of assimilation, etc. of the raw material mixture.

Next, when the pressure is increased to a predetermined pressure, the predetermined solid-liquid ratio (saturation state) is immediately reached, so as soon as this pressure is detected, the valve 01) is opened and the piston (5 ), the pressure inside the crystallization chamber (4) remains constant and the liquid phase flows from the crystallization chamber (4) to the drain tank (6).
) is discharged.

Regarding the discharge of the liquid phase component, the liquid phase component passes through a filter arranged on the inner surface of the body of the crystallization chamber (4), and then passes through the pressure reducing mechanism 00.
and a drain tank (
6). In addition, the rate of liquid phase discharge is
It changes depending on the pressure at the time of discharge, the diameter of the pressure reduction nozzle used as the pressure reduction mechanism 00), etc.

Further, as the piston (5) continues to descend, the crystal grains in the crystallization chamber (4) are compressed and the remaining liquid between the crystal grains is discharged into the drain tank (6) through the so-called "squeezing action". be done.

As the piston (5) continues to descend further, the grains are formed into a large lumpy solid product following the shape of the crystallization chamber (4), thus almost completely discharging the liquid from the solid. At the stage of separation, the liquid phase pressure in the crystallization chamber (4), which is connected to the drain tank (6) under atmospheric pressure, gradually decreases, so that the crystal surface partially melts, resulting in so-called A "sweat wash" is performed and the bulk solid product is purified.

When the pressure of the waste liquid discharged from the crystallization chamber (4) decreases to a predetermined pressure, the piston (5) stops descending, and at the same time the piston begins to rise, the high pressure container (1) also rises. , the solid product is removed from the container (1) while being placed on the lower lid (2). This is the product removal device (
(not shown), lower the high-pressure container (1) and attach it to the lower lid (2), and then return to the raw material injection process.
The same process will be repeated.Before injecting the raw material, purge the remaining liquid in the overflow pipe 09 with a gas inert to the product, such as nitrogen gas, and then Prepare for full liquid detection.

By repeating the above steps, products are produced continuously.

(Problems to be Solved by the Invention) As described above, in the conventional pressure crystallization method, a mixture is pressurized in a high-pressure container to form a solid-liquid coexistence state, the solid-liquid is separated, and the mixture is compressed. After forming a solid product, the product is taken out.

Among the above steps, the solid-liquid separation step involves discharging the liquid phase component under pressure to the outside of the high-pressure container via a filter. In this process, the rate of liquid phase discharge greatly affects the yield and yield of the product.

In other words, when this speed is high, the time required for the solid-liquid separation process is shortened, so the time required for the entire process (one cycle) is shortened, and therefore the production amount per unit time (yield
) becomes larger. On the other hand, the in-phase filter (crystal)
becomes easier to pass through, thereby reducing the yield.

If the liquid phase discharge rate is low, the yield will be small and the yield will be high. Crystals are more likely to be captured by the filter,
This is because the crystal layer further functions as a filter.

Therefore, in view of the yield and yield of the product, the rate of liquid phase discharge that is considered to be optimal is selected, the diameter of the vacuum nozzle is selected accordingly, and the vacuum nozzle is used.

However, when pressure crystallization is actually performed, the yield of the product is high but the yield is small, and it cannot be said that the two are necessarily in balance. The liquid phase discharge rate is selected based on the results of , and the diameter of the vacuum nozzle is selected accordingly, and the vacuum nozzle is used. After repeating this process of trial and error several times, the liquid phase discharge speed and the corresponding diameter of the depressurizing nozzle were finally determined.

Therefore, before the diameter of the pressure reducing nozzle is finally decided,
There is a problem in that it is necessary to repeat trial and error several times, and the pressure reducing nozzle must be attached and removed each time. This is an extremely serious and serious problem in the pressure crystallization method, in which a time reduction of several seconds is desired from the viewpoint of productivity.

In addition, there is a problem in that it is unclear whether the speed of liquid phase discharge corresponding to the finally determined aperture of the depressurizing nozzle is optimal in terms of product yield and yield for the following reasons. . This problem leads to the problem that it is difficult to obtain optimum product yield and yield.

That is, the pressure crystallization carried out before the diameter of the pressure reducing nozzle was finally decided had a small yield of product, or the yield of the product was small, so it was natural to undergo dozens of trials and errors. This is because it cannot be repeated hundreds of times. Furthermore, even if the process is repeated many times, it is thought that the optimal rate of liquid phase discharge may change over time, and a single pressure reducing nozzle alone cannot follow such changes over time. That's because you don't get it.

The present invention has been made in view of these circumstances, and its purpose is to solve the above-mentioned problems of the conventional ones, and to make it possible to install and remove the pressure reducing nozzle through trial and error. The present invention aims to provide a pressure crystallization method that can clarify the optimum liquid phase discharge rate in terms of product yield and yield.

(Means for Solving the Problems) In order to achieve the above object, the present invention provides a pressure crystallization method having the following configuration. That is, the method of the first claim supplies a mixture of two or more components including a specific component to a high-pressure container, pressurizes the mixture in the container to form a solid-liquid coexistence state, and then The liquid phase is discharged to the outside of the container under pressure to separate solid and liquid, and then the remaining liquid is squeezed out by squeezing and discharged to the outside of the container to form a solid product with a specific component in the container. In the pressure crystallization method in which the product is taken out from the container after the liquid is removed, the liquid phase is discharged by controlling the liquid phase discharge speed using a stepless variable speed mechanism having variable resistance to the fluid. This is a pressure crystallization method.

The method according to the second claim is the pressure crystallization method according to the first claim, wherein the liquid phase discharge rate is adjusted to an optimal value of the liquid phase discharge rate based on the yield and yield of the product. .

(Function) As explained above, in the pressure crystallization method according to the present invention, the liquid phase component is discharged by controlling the liquid phase component discharge speed using a stepless variable speed mechanism having variable resistance to the fluid. Therefore, the liquid phase component discharge rate can be kept constant or can be changed over time.

On the other hand, when we examined the effect of liquid phase discharge rate on product yield and yield, we found that at the beginning of liquid phase discharge, the crystal trapping layer on the filter surface is thin, so crystals also pass through the filter, and the discharge progresses. We found that as the crystal trapping layer becomes thicker, it becomes difficult for even fine crystals to pass through the filter.

In addition, for this reason, we have found that it is desirable to reduce the liquid phase discharge rate at the beginning of liquid phase discharge and increase the liquid phase discharge rate as discharge progresses from the viewpoint of product yield and yield. Obtained.

As mentioned above, the optimum liquid phase discharge rate is not constant but changes over time, and the pressure crystallization method according to the present invention can change the liquid phase discharge rate over time as described above. It becomes possible to adjust the liquid phase component discharge rate to an optimum value.

The pressure crystallization method according to the present invention is carried out, for example, as follows. That is, first, a first pressure crystallization is performed to determine the yield and yield of the product. The liquid phase component discharge rate at this time is made to follow the temporal change in the liquid phase component discharge rate that is considered to be optimal in terms of the yield and yield of the product.

The second pressure crystallization is performed by selecting the temporal change in the liquid phase discharge rate that is considered optimal based on the previous results, and by making the actual liquid phase discharge rate follow that change over time. Determine yield and yield. However, other conditions are the same as last time.

This trial and error process is repeated several times to finally determine the change in liquid phase discharge rate over time.

Therefore, by repeating this trial and error process, it becomes possible to clarify the optimum liquid phase discharge rate in terms of product yield and yield. Alternatively, it becomes possible to determine a liquid phase component discharge rate that is suitable for the purpose.

Furthermore, since the liquid phase discharge speed is controlled by the continuously variable transmission mechanism as described above, there is no need to attach and remove the pressure reducing nozzle through trial and error as in the conventional method.

In addition, it is desirable to adjust the liquid phase discharge rate to the optimum liquid phase discharge rate based on the yield and yield of the product.
This is because the desired yield and amount of the product can be obtained.

(Example) The apparatus used in Example 1 was the same as that shown in FIG. 1, with some exceptions. That is, in place of the pressure reducing mechanism 00 in FIG. 1, that is, the pressure reducing nozzle, a continuously variable transmission mechanism having variable resistance to fluid is provided.

The main parts of this continuously variable transmission mechanism are shown in FIG. As can be seen in FIG. 2, this main part consists of a nozzle body surface, a lenticular valve seat 09) with a large side, and a conically shaped bottle QID or valve stem. The pin (c) is moved up and down in the drawing by a drive device (not shown) to open and close the hole θF.

That is, the size of the gap between the bottle QO and the lenticular valve seat 09) can be changed steplessly. Pipes (9) are connected before and after the transmission mechanism, and fluid enters from below the large side and flows upward. In the figure, N is a holding material for the lens-shaped valve seat 09), P is a seal packing, Ps is a packing pressing material, Li, and L.

indicates a fluid.

The raw material mixture is a cresol solution consisting of 80% p-cresol and the remainder t-cresol.

First, the above cresol solution is cooled in a pre-crystallization can (7), poured into a crystallization chamber (4), and then pressurized to 1500 atm, and then the liquid phase is removed from the container under a pressure of 1500 atm. Then, after squeezing out the remaining liquid and discharging it, a homogeneous product containing a specific component was taken out from the container. The liquid phase discharge rate in the solid-liquid separation step was controlled by a continuously variable transmission mechanism and adjusted to a target liquid phase discharge rate. Figure 3 shows the target and actual speed. In FIG. 3, the dotted line indicates the target speed, and the solid line indicates the actual speed (the same applies hereinafter). As shown in this figure, the liquid phase discharge rate changes over time.

As a result of the first pressure crystallization, the yield of the product (p-cresol) was 35.6x, and the yield was 15.3 g/inch.

The second pressure crystallization was carried out by setting a target speed for discharging the liquid phase component, which was considered to be optimal, based on the above-mentioned previous results, and making the actual liquid phase component discharge speed follow the target speed. The target and actual speeds are shown in FIG.

Conditions other than the above discharge rate are the same as those in the first pressure crystallization. As a result, the product yield was 36.3χ,
The yield was 14.5g/rain.

Pressure crystallization as described above was repeated, and in the fifth pressure crystallization, product yield: 36.3X, yield:
A result of 17.5 g/a+in was obtained.

The time required to complete this fifth pressure crystallization is:
It was shortened to 1/10 of the case of Comparative Example 1 described later.

The apparatus used in Comparative Example 1 was the same as that shown in FIG. That is, a pressure reduction nozzle was used for the pressure reduction mechanism 0ω, and was replaced with one of a different diameter each time pressure crystallization was performed. Its caliber is
It is 0.10-0.45m+*φ.

By replacing the pressure reduction nozzle, the liquid phase discharge speed changes each time pressure crystallization is performed. The conditions other than the liquid phase discharge rate are the same as those in the first pressure crystallization of Example 1.

The liquid phase discharge rate in the first pressure crystallization was 0.3
1/win. Product yield is 37.5! The yield was 14.8 g/min.

The liquid phase discharge rate in the second pressure crystallization was 0.9
1/win. The product yield was 34.5x and the yield was 16.8g/win.

Although the pressure crystallization described above was repeated 25 times, the same yield and amount of product as in the 5th time of Example 1 could not be obtained, and the yield of the product in the 25th time was 36.0χ , collection
is 17.0g/win.

Further, the time required to complete the 25th pressure crystallization was 20 times that of Example 1.

Also, the time required up to the fifth test was 10 times that of Example 1. This is because it took time to replace the pressure reducing nozzle.

(Effects of the Invention) According to the pressure crystallization method according to the present invention, when determining the optimum liquid phase discharge rate in the solid-liquid separation step, there is no need to replace the decompression nozzle due to the conventional trial and error process. Therefore, it becomes possible to clarify the optimum liquid phase component discharge rate from the viewpoint of product yield and yield.

[Brief explanation of drawings]

Figure 1 is a diagram showing the process flow and the concept of the device related to the pressure crystallization method, Figure 2 is a diagram showing the main parts of the continuously variable transmission mechanism that has variable resistance to fluid, and Figure 3 is the liquid phase discharge speed. It is a diagram showing the goals and results of. (1) - Pressure vessel (2) - Lower M (3) - Hydraulic unit (4) - Crystallization chamber (5) - Piston (6) - Drainage tank (7) - Preliminary crystallizer (8) - Raw material Supply pump (9) side - Piping 00) - Pressure reduction mechanism 000210
6) - Valve 04) - [R tank 0ω - Overflow pipe 07) - Nozzle body 08) - 6 〇! [1-Lenticular valve seat (to)-conical pin N-valve seat a holding material P-seal packing Ps-packing holding material Li,
Lo - One-fluid patent applicant Kobe Steel Co., Ltd. Agent Patent attorney Akira Kanemaru - Figure 3 Shiko Button &'l (5e6) Za0

Claims (2)

[Claims] (1) A mixture of two or more components including a specific component is supplied to a high-pressure container, the mixture is pressurized in the container to form a solid-liquid coexistence state, and then the liquid phase is removed under pressure. After forming a solid product with a specific component in the container by discharging it outside the container to separate solid and liquid, and then squeezing out the residual liquid and discharging it outside the container, the product is removed from the container. 1. A pressure crystallization method for extracting a liquid phase component, characterized in that the liquid phase component is discharged by controlling the liquid phase component discharge speed using a stepless variable speed mechanism having variable resistance to the fluid. (2) The pressure crystallization method according to claim 1, wherein the liquid phase discharge rate is adjusted to an optimal value based on the yield and amount of the product.