JPH0779924B2 - Pressure crystallizer - Google Patents

Description

TECHNICAL FIELD The present invention relates to a pressure crystallizer.

(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 been attracting a great deal of attention as the chemical industry has become finer in recent years because of its easy yield and low energy consumption.

An outline of such pressure crystallization method is, for example, Volume 50 of Chemical Industry (19
1986) Page 331 "Outline of pressure crystallization method and equipment". An example of the process flow and apparatus of such pressure crystallization method is shown in FIG. FIG. 7 shows a cross-sectional view of the main parts of the raw material supply line in the apparatus. As shown in FIG. 6, the pressure vessel (1) is provided with a lid (lower lid) (2) below, and the piston (5) is moved in the vessel (1) by the operation of the hydraulic unit (3). The piston (5) and the lower lid (2) are provided so as to move up and down, and a crystallization chamber (4) is formed in the pressure vessel (1). 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). Further, the crystallization chamber (4) and the pressure crystallization raw material adjusting storage tank (7) are connected by a raw material supply pipe (19) via a raw material supply pump (8) and a liquid supply valve (12), A raw material supply line (13) is formed.
As shown in FIG. 7, the liquid supply valve (12) is a so-called check valve, and is composed of a valve seat (17) and a valve rod (18). The raw material supply pipe (19) is bent at a right angle in the lower lid (2). In the figure, (21) shows a member screwed into the pressure vessel (1) and forms a part of the pressure vessel.

In this apparatus, the raw material is fed from the raw material tank (14) to the adjustment storage tank (7), where it is cooled to generate a seed crystal 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. Because there is a risk that
When the liquid is supplied in a slurry state containing seed crystals, there is an advantage that not only is there no concern about such supersaturation pressure, but also crystal growth can be expected without generation of nuclei due to pressurization.

Next, the raw material supply line (13) is used to feed the raw material into the crystallization chamber (4).
Inject. When the raw material is filled in the crystallization chamber (4), the liquid starts to flow out through the overflow pipe (15) having an opening at the piston tip.
2) Close the valve (16) and start pressurization by the piston (5). 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 with the progress of solidification, the pressure crystallization method generally does not perform cooling to prevent this temperature rise, and 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, generally, a predetermined solid-liquid ratio (saturated state) is immediately reached. Therefore, as soon as this pressure is detected, the valve (11) is opened and the hydraulic unit (3) moves to the piston (5). When the piston continues to descend while the pressure acting on the) is maintained, the liquid phase is transferred from the crystallization chamber (4) to the drain tank (6) while the pressure inside the crystallization chamber (4) is kept constant. Is discharged.

When the piston (5) is further continued to descend, the crystal grains in the crystallization chamber (4) are pressed and squeezed, and the residual liquid between the crystal grains is subjected to a so-called "squeeze action" and discharged to the drainage tank (6). To be done. 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). In this way, at the stage of almost completely separating the liquid from the solid, the drainage tank (6) under atmospheric pressure
Since the liquid phase pressure in the crystallization chamber (4) communicating with the gradual drop gradually, the crystal surface is partially melted, so-called "perspiration cleaning" is performed, and the solid 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.

In addition, the raw material tank and the adjustment storage tank may not be separate as described above but may be combined and used as one. Depending on the raw material, there may be only the raw material tank or only the adjustment storage tank. The container (raw material tank or adjustment storage tank) in such a case is also called an adjustment storage tank in a broad sense.

(Problems to be Solved by the Invention) As described above, the conventional pressure crystallizer has the adjustment storage tank for the pressure crystallization raw material, the high-pressure container, the means for pressurizing the inside of the high-pressure container, and the adjustment storage. A pressure crystallizer having a raw material supply line in which a pump and a feed valve are connected in this order between a tank and a high-pressure container. Conventional pressure crystallization method, using the above apparatus, the raw material is injected from the adjusted storage tank through the valve into the high-pressure container, the valve is closed and pressurized to form a solid product, The process of taking out the product is repeated.

However, according to the above-mentioned conventional apparatus, while repeating the pressure crystallization process as described above, the raw material supply line is clogged, the raw material cannot be injected into the high-pressure vessel, or the raw material injection speed is lowered. We often encounter situations where material injection takes a very long 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.

Although warming the raw material supply line can prevent clogging, this method is not suitable as a solution because it causes the disappearance or reduction of extremely important seed crystals.

The present invention has been made by paying attention to such circumstances, and its purpose is to solve the above-mentioned problems of the conventional one, to prevent the blockage of the raw material supply line, and to An object of the present invention is to provide a pressure crystallizer capable of always stably injecting a raw material without lowering the raw material injection rate.

(Means for Solving the Problems) In order to achieve the above object, the present invention provides a pressure crystallizer having the following configuration.

That is, the apparatus according to the first aspect of the present invention comprises a pressure crystallization raw material adjusting reservoir, a high pressure vessel, a means for pressurizing the inside of the high pressure vessel, a pump and a liquid supply valve between the adjusting reservoir and the high pressure vessel. A pressure crystallizer having a raw material supply line pipe-connected in this order and a raw material circulation line branched from the raw material supply pipe and connected to a regulating storage tank through a circulation valve, wherein a valve seat of a liquid supply valve Between the pump and the pump, the raw material circulation line is branched from the bent portion located closest to the valve seat in the bent portion of the raw material supply pipe or between the bent portion and the valve seat. It is a pressure crystallizer.

The apparatus according to the second aspect of the present invention comprises an adjustment storage tank for the pressure crystallization raw material, a high-pressure container, a means for pressurizing the inside of the high-pressure container, a pump and a liquid supply valve between the adjustment storage tank and the high-pressure container. A pressure crystallizer having a raw material supply line pipe-connected in this order and a raw material circulation line branched from the raw material supply pipe and connected to a regulating storage tank through a circulation valve, wherein the raw material supply line is a supply line. The pressure crystallizer is characterized in that it extends linearly between the valve seat of the liquid valve and the pump, and the raw material circulation line branches from the linear portion.

(Operation) As a result of an experimental study on the cause of the blockage of the raw material supply line as described above, it was found that the above blockage occurred due to the precipitation and accumulation of seed crystals in the raw material (slurry state) during the period other than the time of raw material supply. Further, it has been found that such precipitation / accumulation is particularly likely to occur inside the pump or the bent portion of the raw material supply line, and by suppressing this, the occurrence of blockage can be prevented.

The above-mentioned precipitation / accumulation inside the pump or in the bent portion can be suppressed if the raw material can be circulated continuously or intermittently in these portions.

Therefore, as described above, the pressure crystallizer according to the present invention (the apparatus according to the first aspect) has a raw material circulation line that branches from the raw material supply pipe and is connected to the adjustment storage tank through the circulation valve. There, from the bent portion located closest to the valve seat in the bent portion of the raw material supply pipe between the valve seat of the liquid supply valve and the pump, or from between the bent portion and the valve seat, The raw material circulation line is branched. This is because the raw material can be circulated continuously or intermittently inside the pump or in the bent portion, and thus the above-mentioned clogging can be prevented.

If the branch point is between the valve seat and the bent portion closest to the valve seat or is the closest bent portion, otherwise, at least the possibility of occurrence of blockage at the closest bent portion occurs. Because.

Further, as described above, the pressure crystallizer according to the present invention (the apparatus according to the second aspect) is arranged such that the raw material supply line extends linearly between the valve seat of the liquid supply valve and the pump, and The raw material circulation line was made to branch off from the straight portion. This is because the raw material can be continuously or intermittently circulated inside the pump or in the bent portion, and the above-mentioned clogging can be prevented.

(Example) Example 1 FIG. 1 shows a schematic view of a main part of an apparatus according to Example 1. First
As can be seen from the figure, this device has a raw material circulation line (20), which is branched from the bent portion (B) closest to the valve seat (17) of the liquid supply valve. In the figure, (22) shows a valve for opening and closing the flow path of the raw material circulation line (20). Other parts are the same as those shown in FIG. This device is one in which the piston of the pressurizing means operates in the vertical direction (hereinafter referred to as a vertical device).

Using a cresol solution consisting of p-cresol 80% and the balance m-cresol as a raw material, pressure crystallization was carried out using p-cresol as a product.

First, the above raw material is cooled in the adjustment storage tank (7) and injected into the crystallization chamber (4) through the raw material supply line (13) by the raw material supply pump (8), and then pressurized to 1500 atm, and then 15
The liquid phase was discharged to the outside of the container under a pressure of 00 atm for solid-liquid separation. Then, after squeezing to squeeze out the residual liquid and discharging it, the solid product of the specific component was taken out from the container. Then return to the raw material injection process, repeat the same process 30 times,
The product was produced continuously.

As a result of the above pressure crystallization, it was possible to always stably inject the raw material without lowering the rate of injecting the raw material into the high-pressure vessel. This is because the raw material supply line was not blocked at all.

Example 2 FIG. 2 shows a schematic view of a main part of an apparatus according to Example 2. This device is a vertical device. As can be seen from FIG. 2, this device has a raw material circulation line (20), which is located near the bent portion (B) and valve seat (17) closest to the valve seat (17) of the liquid feed valve. It is a branch from between and. The branch point is indicated by (S) in the figure. Other parts are similar to those of the device according to the first embodiment.

The same steps as in Example 1 were repeated 30 times using the above apparatus. As a result, the raw material could always be stably injected.

Example 3 FIG. 3 shows a schematic view of a main part of an apparatus according to Example 3. This device is a vertical device. As can be seen from FIG. 3, in this device, the raw material supply line (13) is linear between the valve seat (17) of the liquid feed valve and the pump (8), and the raw material circulation line (20) ) Is to branch.
The branch point is indicated by (S) in the figure. Other parts are similar to those of the device according to the first embodiment.

The same steps as in Example 1 were repeated 30 times using the above apparatus. As a result, it was possible to always perform stable raw material injection.

Example 4 FIG. 4 shows a schematic view of a main part of an apparatus according to Example 4. This device is a horizontal device in which the piston moves horizontally. As can be seen from FIG. 4, this device is one in which the raw material circulation line (20) is branched from between the bent portion (B) closest to the valve seat (17) of the feed valve and the valve seat (17). . The branch point is indicated by (S) in the figure. The devices used in the other parts are the same as those in the first embodiment.

The same steps as in Example 1 were repeated 30 times using the above apparatus. As a result, the raw material could always be stably injected.

Example 5 FIG. 5 shows a schematic view of a main part of an apparatus according to Example 5. This device is a vertical device. As can be seen from FIG. 5, in this device, the raw material supply line (13) is linear between the valve seat (17) of the liquid supply valve and the adjustment reservoir (7), and the valve seat (1
The raw material circulation line (20) is branched from between the pump (7) and the pump (8). The branch point is (S) in the figure
Indicated by. Other parts are similar to those of the device according to the first embodiment.

The same steps as in Example 1 were repeated 30 times using the above apparatus. As a result, the raw material could always be stably injected.

Comparative Example 1 The apparatus used in Comparative Example 1 is the same as that shown in FIG. That is, it does not have a raw material circulation line. With this apparatus, the same steps as in Example 1 were repeated. As a result, the raw material injection rate started to decrease at the time of repeating 5 times,
Raw material injection became impossible after repeating 18 times (Effect of the invention) According to the pressure crystallizer according to the present invention, it is possible to prevent the raw material supply line from being blocked, and to reduce the raw material injection rate into the high-pressure vessel. The raw material injection can always be carried out stably without inviting.

[Brief description of drawings]

FIG. 1 is a schematic view of a main part of the apparatus according to the first embodiment, FIG. 2 is a schematic view of a main part of the apparatus according to the second embodiment, and FIG. 3 is a schematic view of a main part of the apparatus according to the third embodiment. FIG. 5 is a schematic view of a main part of an apparatus according to Example 4, and FIG. 5 is a schematic view of a main part of an apparatus according to Example 5.
FIG. 6 is a diagram showing a concept of a process flow and a device relating to a conventional pressure crystallization method, and FIG. 7 is a sectional view of a main part of a raw material supply line in the conventional pressure crystallization device. (1) …… Pressure vessel, (2) …… Lower lid (3) …… Hydraulic unit, (4) …… Crystallization chamber (5) …… Piston, (6) …… Drainage tank (7)… Material storage tank (8) Material supply pump (9) Piping, (10) Pressure reducing mechanism (11) (16) (22) Valve, (12) Liquid supply valve (13) …… Raw material supply line, (14) …… Raw material tank (15) …… Overflow pipe, (17) …… Valve seat of liquid supply valve (18) …… Valve of liquid supply valve, (19) Material feed pipe (20) Material circulation line (21) Pressure vessel member (B) Bend, (S) Branch point

Claims (2)

[Claims] 1. A controlled storage tank for pressure crystallization raw material, a high-pressure vessel, a means for pressurizing the inside of the high-pressure vessel, and a pump and a liquid supply valve are connected in this order between the adjusted storage tank and the high-pressure vessel. A raw material supply line and a raw material circulation line that branches from the raw material supply pipe and is connected to a regulating reservoir via a circulation valve, the pressure crystallizing device being provided between a valve seat of a liquid supply valve and a pump. Pressure crystallizer, characterized in that the raw material circulation line is branched from the bent portion located closest to the valve seat in the bent portion of the raw material supply pipe or between the bent portion and the valve seat. . 2. A regulating storage tank for a pressure crystallization raw material, a high-pressure vessel, a means for pressurizing the inside of the high-pressure vessel, a pump and a liquid supply valve are connected in this order between the adjusting storage vessel and the high-pressure vessel. A raw material supply line and a raw material circulation line branched from the raw material supply pipe and connected to a regulating storage tank through a circulation valve, wherein the raw material supply line is a valve seat of a liquid supply valve. And a pump, and the raw material circulation line is branched from the linear portion.