JPH082403B2 - Pressure crystallization method - Google Patents

Description

Description: TECHNICAL FIELD The present invention relates to a pressure crystallization method, and more specifically, a pressure crystallization method for controlling and adjusting the rate of liquid phase component discharge in a solid-liquid decomposition step. Regarding

(Prior Art) The pressure crystallization method has great potential for application to a raw material system that is difficult to separate by the conventional distillation method or cooling crystallization method, that a high-purity product is easily obtained, and It is a separation and purification technology that has received a great deal of attention with the recent refinement of chemical factories because it is easy to obtain a yield and consumes less energy.

An outline of such a pressure crystallization method is described in, for example, Chemical Industry Volume 50 (1986), p.331, "Outline of Pressure Crystallization Method and Apparatus". This will be described with reference to FIG. 1 (a diagram showing the concept of the process flow and the apparatus). The pressure vessel (1) is provided with a lid (lower lid) (2) below and the piston (5) is a hydraulic unit. It is provided so as to move up and down in the container (1) by the operation of (3), and the crystallization chamber (4) is provided in the pressure container (1) by the piston (5) and the lower lid (2). It is formed. The crystallization chamber (4) and the drainage tank (6) are connected by a pipe (9) via a pressure reducing mechanism (10) and a valve (11). The crystallization chamber (4) and the preliminary crystallization can (7) are connected by a pipe (13) via a raw material supply pump (8) and a valve (12).

A filter (not shown) is provided on the inner surface of the body of the crystallization chamber (4). In addition, the pressure reducing mechanism (1
0) is provided for adjusting the liquid phase component discharge speed described later, and an orifice having a small diameter, that is, a decompression nozzle is used. This caliber is, for example, 0.10 to 0.45 mmφ,
The diameter is selected according to the target liquid phase discharge speed. Caliber 0.10φ is the smallest diameter that can be produced.

In this apparatus, the raw material is supplied from the raw material tank (14) to the preliminary crystallization can (7), where it is cooled to generate seed crystals for pressure crystallization. This is because when the raw material without containing seed crystals is subjected to pressure crystallization, the supersaturation pressure in pressure crystallization is generally relatively high, at several hundred atmospheres or higher, and high pressure is required for initial crystal formation. When a slurry containing seed crystals is supplied, there is an advantage that there is no concern about such supersaturation pressure and that crystal growth can be expected without pressurization.

Next, the raw material is injected into the crystallization chamber (4) from the pipe (13) through the valve (12). When the crystallization chamber (4) is filled with the raw material, the liquid begins to flow out through the overflow pipe (15) having an opening at the tip of the piston. When this is detected, the valves (12) and (16) are closed. Pressurization by the piston (5) is started. When the raw material liquid is pressurized, crystallization of the specific substance in the raw material proceeds, and the inside of the crystallization chamber (4) is in a solid-liquid equilibrium state under high pressure. The solid formed at this time is generally an extremely high-purity substance. Although the temperature in the crystallization chamber (4) rises due to the latent heat of solidification generated as the solidification proceeds, the pressure crystallization method generally does not perform cooling to prevent this temperature rise, but adiabatically applies it. The method of pressing is adopted. The temperature reached after the temperature is raised, that is, the solid-liquid separation start temperature affects the purity and yield of the product. Therefore, this is adjusted by the liquid supply temperature in consideration of the specific heat of the raw material mixture, the latent heat of solidification and the like.

Next, when the pressure is increased to a predetermined pressure, a predetermined solid-liquid ratio (saturated state) is generally reached immediately. Therefore, as soon as this pressure is detected, the valve (11) is opened and the hydraulic unit (3) is opened.
When the piston continues to descend while the pressure acting on the piston (5) from the crystallization chamber (4) is kept constant, the liquid phase is discharged from the crystallization chamber (4) to the drain tank. It is discharged to (6).

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 a pipe (9) through a pressure reducing mechanism (10) and a valve (11). Is guided to the drainage tank (6). The speed of discharging the liquid phase component changes depending on the pressure at the time of discharging and the diameter of the pressure reducing nozzle used as the pressure reducing mechanism (10).

When the piston (5) continues to descend, the crystallization chamber (4)
The crystal grains in the inside are compressed under pressure, and the residual liquid between the crystal grains undergoes a so-called "squeeze action" and is discharged to the drainage tank (6).

As the piston (5) is further lowered, the crystal grains are formed into one large lump solid product along the shape of the crystallization chamber (4). When the liquid is almost completely separated from the solid in this way, the liquid phase pressure in the crystallization chamber (4) communicating with the drainage tank (6) under atmospheric pressure gradually decreases. The crystal surface is partially melted, a so-called "perspiration cleaning" is performed, and a lump solid product is purified.

When the pressure of the waste liquid discharged from the crystallization chamber (4) drops to a predetermined pressure, the lowering of the piston (5) is stopped, the ascent of the piston is started, and the high-pressure container (1) is also raised. The solid product is taken out of the container (1) while being placed on the lower lid (2). This is taken out by a product take-out device (not shown), the high-pressure container (1) is lowered and attached to the lower lid (2), and then the process of injecting the raw material is repeated and the same process is repeated. In addition, prior to the injection of raw materials, the residual liquid in the overflow pipe (15) is purged with a gas such as nitrogen gas that is inert to the product, and preparations for full liquid detection at the time of injection in the next process are made. Keep it.

By repeating the above steps, products are continuously produced.

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

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

That is, when this speed is high, the time required for the solid-liquid separation step is shortened, so that the time required for all steps (1 cycle) is shortened, and therefore the production amount (yield) per unit time is increased. On the other hand, the solid phase component (crystal) easily passes through the filter, which reduces the yield.

When the liquid phase component discharge rate is low, the yield is low and the yield is high. This is because the crystals are more likely to be captured by the filter portion, and the crystal layer further exhibits the function as a filter.

Therefore, in view of the yield of the product and the yield, the optimal liquid phase component discharge speed is selected, the diameter of the pressure reducing nozzle is selected accordingly, and the pressure reducing 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 in harmony. Therefore, the next pressure crystallization is performed by using the pressure reducing nozzle by selecting the liquid phase component discharge speed based on the result of the previous time, selecting the pressure reducing nozzle diameter accordingly. By repeating this trial and error several times, the liquid phase component discharge speed and the diameter of the decompression nozzle corresponding thereto are finally determined.

Therefore, trial and error must be repeated several times before the diameter of the decompression nozzle is finally determined, and the decompression nozzle must be attached and detached each time. This is a very serious and serious problem in the pressure crystallization method in which it is desired to shorten the time by several seconds from the viewpoint of productivity.

In addition, there is a problem that it is unclear whether the rate of liquid phase component discharge corresponding to the finally determined decompression nozzle diameter is optimal in view of product yield and yield due to the following reasons. . This problem leads to a problem that it is difficult to obtain the optimum product yield and the yield.

That is, the pressure crystallization carried out until the diameter of the depressurizing nozzle is finally determined is such that the product yield is small, or
This is because the product yield is so small that trial and error cannot be repeated tens or hundreds of times. or,
Even if a large number of repetitions are performed, it is considered that the optimal liquid phase component discharge rate may change with the passage of time, and it is not possible to follow such changes with time with only one depressurizing nozzle. Because.

The present invention has been made by paying attention to such a situation, and an object thereof is to solve the above-mentioned problems of the conventional one, without attaching and detaching the decompression nozzle due to trial and error. Another object of the present invention is to provide a pressure crystallization method capable of clarifying the optimal liquid phase component discharge rate from the viewpoint 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 is to supply a mixture of two or more components containing a specific component to a high-pressure container, pressurize the mixture in the container to form a solid-liquid coexisting state, and The liquid component was discharged under pressure to the outside of the container for solid-liquid separation, and then squeezed to squeeze out the residual liquid and discharged outside the container to form a solid product of the specific component in the container. After that, in the pressure crystallization method for taking out the product from the container, the liquid crystal component is discharged by controlling the liquid phase component discharge speed by a continuously variable transmission mechanism having a variable resistance to the fluid. This is the analysis method.

The method according to claim 2 is the pressure crystallization method according to claim 1, wherein the liquid phase component discharge rate is adjusted to an optimum value of the liquid phase component discharge rate based on the product yield and the yield. .

(Operation) The pressure crystallization method according to the present invention, as described above,
Since the liquid phase component discharge speed is controlled by the stepless speed change mechanism having variable resistance to the fluid, the liquid phase component discharge speed can be made constant, or can be changed over time. Like

On the other hand, when the effect of the liquid phase component discharge rate on the product yield and the yield was examined, the crystals passed through the filter at the beginning of the liquid phase component discharge, so the crystals also passed through the filter and the discharge progressed. As a result, the crystal trapping layer becomes thicker, and it has been found that it becomes difficult for even fine crystals to pass through the filter. Therefore, from the viewpoint of product yield and yield, it was found that it is desirable to reduce the liquid phase component discharge rate at the initial stage of liquid phase component discharge and increase the liquid phase component discharge rate as the discharge progresses. Obtained.

As described above, the optimal liquid phase component discharge rate is not constant,
Since the pressure crystallization method according to the present invention can change the liquid phase component discharge rate with time as described above, it can be adjusted to an optimum liquid phase component discharge rate.

The pressure crystallization method according to the present invention is performed, for example, as follows. That is, first, the first pressure crystallization is performed to obtain the product yield and the yield. The liquid phase component discharge rate at this time is made to follow the change with time of the liquid phase component discharge rate which is considered to be optimal in view of the product yield and the yield.

The second pressure crystallization was performed by selecting the time-dependent change in the liquid phase component discharge rate considered to be optimal based on the previous results, and making the actual liquid phase component discharge rate follow the time change. Determine the yield and yield. However, other conditions are the same as the previous time.

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

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

Further, since the liquid phase component discharge speed is controlled by the continuously variable transmission mechanism as described above, it is not necessary to attach and detach the depressurizing nozzle due to trial and error as in the conventional method.

Incidentally, it is desirable to adjust the liquid phase component discharge rate to an optimum value of the product phase and the liquid phase component discharge rate based on the yield. This is because the desired product yield and yield can be obtained.

(Example) Example 1 The apparatus used in Example 1 is the same as that shown in FIG. 1 except for a part. That is, instead of the pressure reducing mechanism (10) of FIG. 1, that is, the pressure reducing nozzle, a continuously variable transmission mechanism having a variable resistance to fluid is provided. The main part of this continuously variable transmission mechanism is shown in FIG. As can be seen in FIG. 2, this main part consists of a nozzle body (17), a lenticular valve seat (19) with a hole (18) and a conical pin (20) or valve stem. The pin (20) moves up and down in the drawing by a driving device (not shown) to open and close the hole (18). That is, the size of the gap between the pin (20) and the lens-shaped valve seat (19) can be continuously changed. A pipe (9) is connected to the front and rear of the speed change mechanism, and the fluid enters from below the hole (18) and flows upward. In the figure, N is a pressing member for the lens-like valve seat (19), P is a seal packing, Ps is a packing pressing member, and Li and Lo are fluids.

The mixture of raw materials is a cresol solution composed of 80% p-cresol and the balance m-cresol.

First, the cresol solution was cooled in a preliminary crystallization can (7), poured into the crystallization chamber (4), and then pressurized to 1500 atm,
Subsequently, the liquid phase was discharged to the outside of the container under a pressure of 1500 atm for solid-liquid separation. Then, squeeze to remove the residual liquid,
After discharging, a solid product having specific components was taken out from the container. In addition, the liquid phase component discharge speed in the solid-liquid separation step was controlled by a continuously variable transmission mechanism and adjusted to a target liquid phase component discharge speed. FIG. 3 shows the target and actual speeds. Third
In the figure, the dotted line shows the target speed and the solid line shows the actual speed (the same applies hereinafter). As shown in this figure, the liquid phase component discharge rate has a change with time.

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

The second pressure crystallization was performed by setting the target speed of liquid phase component discharge considered to be optimum based on the result of the previous time and following the actual liquid phase component discharge speed. The target and actual speed are shown in FIG. The conditions other than the discharge rate are the same as the conditions in the first pressure crystallization. As a result, the product yield was 36.3%, and the yield was 14.5 g / min.

Repeated pressure crystallization as described above, in the fifth pressure crystallization, product yield: 36.3%, yield: 17.5 g / min
I got the result.

The time required to complete the fifth pressure crystallization was shortened to 1/10 of that in Comparative Example 1 described later.

Comparative Example 1 The apparatus used in Comparative Example 1 is the same as that shown in FIG. That is, a depressurizing nozzle was used as the depressurizing mechanism (10), and each time the pressure crystallization was performed, the pressure was changed to a different one. The diameter is 0.10 to 0.45 mmφ.

By exchanging the above-mentioned depressurizing nozzle, the liquid phase component discharge rate changes every time pressure crystallization occurs. The conditions other than this liquid phase component discharge rate are the same as the conditions in the first pressure crystallization of Example 1.

The liquid phase discharge rate in the first pressure crystallization was 0.3.
/ min. Product yield 37.5%, yield 14.8g / min
Met.

The liquid phase discharge rate in the second pressure crystallization was 0.9.
/ min. Product yield 34.5%, yield 16.8g / min
Met.

The pressure crystallization as described above was repeated 25 times, but the same yield and yield of the product as in the case of the fifth time of Example 1 were not obtained, and the yield of the 25th product was 36.0%. Yield 17.0
It was g / min.

The time required to complete the 25th pressure crystallization was 20 times that in the case of Example 1.

In addition, the time taken until the fifth time is also the same as in the first embodiment.
It was 10 times that of. This is because it took time to replace the decompression nozzle.

(Effect of the Invention) According to the pressure crystallization method of the present invention, when the optimum liquid phase component discharge rate in the solid-liquid separation step is obtained, the decompression nozzle is replaced by conventional trial and error. However, the optimum liquid phase component discharge rate can be defined from the viewpoint of product yield and yield.

[Brief description of drawings]

FIG. 1 is a diagram showing a process flow and a concept of an apparatus related to a pressure crystallization method, FIG. 2 is a diagram showing a main part of a continuously variable transmission mechanism having a variable resistance to a fluid, and FIG. 3 is a liquid phase component discharge speed. It is a figure which shows the target and performance. (1) ...... Pressure vessel, (2) ...... Lower lid, (3) ...... Hydraulic unit (4) ...... Crystallization chamber, (5) ...... Piston, (6) ...... Drainage tank (7) ...... Preliminary crystallization can, (8) …… Raw material supply pump (9) (13) …… Piping, (10) …… Decompression mechanism, (11)
(12) (16) …… Valve (14) …… Material tank, (15) …… Overflow pipe (17) …… Nozzle body, (18) …… Hole, (19) …… Lens valve seat (20 ) …… Conical pin, N …… Pressing material for valve seat (19) P …… Seal packing, Ps …… Packing pressing material Li, Lo …… Fluid

Claims (2)

[Claims] 1. A mixture of two or more components containing a specific component is supplied to a high-pressure container, and the mixture is pressurized in the container to form a solid-liquid coexisting state, and subsequently, a liquid phase under pressure is applied. Of the specific component is discharged to the outside of the container by solid-liquid separation, and then squeezed to squeeze out the residual liquid to form a solid product of the specific component in the container. In the pressure crystallization method for extracting the product, the liquid phase component is discharged by controlling the liquid phase component discharge speed by a stepless speed change mechanism having a variable resistance to the fluid. 2. The pressure crystallization method according to claim 1, wherein the liquid phase component discharge rate is adjusted to an optimum value of the product phase and the liquid phase component discharge rate based on the yield.