JPH0698245B2 - Pressure crystallizer - Google Patents

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a pressure crystallizer, and in particular, it is possible to easily and surely control a filtration rate,
The present invention relates to a pressure crystallizer capable of downsizing a pressure reducing mechanism in a liquid phase discharge pipe.

[0002]

2. Description of the Related Art The pressure crystallization method has great potential for application to a raw material system that is difficult to separate by conventional distillation methods and cooling crystallization methods, that high purity products are easily obtained, 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 the pressure crystallization method is described in, for example, Kagaku Kogyo, Vol. 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 high-pressure container 1 is provided with a lid (lower lid) 2 below and the piston 5
Is provided so as to move up and down in the container 1 by the operation of the hydraulic unit 3, and the piston 5 and the lower lid 2 form a crystallization chamber 4 in the high pressure container 1. The crystallization chamber 4 and the drainage tank 6 are connected by a liquid phase discharge pipe 9 via a pressure reducing mechanism 10 and a valve 11. The crystallization chamber 4 and the preliminary crystallization can 7 are connected to a pipe 13 via a raw material supply pump 8 and a valve 12.
Are connected by.

A filter (not shown) is arranged on the inner surface of the body of the crystallization chamber 4. Further, the decompression mechanism 10 is provided to reduce the liquid phase component discharge speed described later, and an orifice having a small diameter, that is, a decompression nozzle is used. The diameter is, for example, 0.10 to 0.45 mmφ, and the diameter is selected according to the target liquid phase component discharge speed. The caliber 0.10φ is the minimum diameter that does not usually cause clogging.

In this apparatus, the raw material is fed 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 the liquid is supplied in a slurry state containing seed crystals, there is an advantage that not only there is no concern about such supersaturation pressure, but also crystal growth can be expected without generation of nuclei by 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 starts to flow out through the overflow pipe 15 having an opening at the piston tip. When this is detected, the valves 12 and 16 are closed and the 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. The temperature in the crystallization chamber 4 rises due to the latent heat of solidification generated with the progress of solidification.

When the piston 5 is further lowered, the crystal grain group in the crystallization chamber 4 is compressed under pressure, and the residual liquid between the crystal grains is discharged to the drainage tank 6 under the so-called "squeezing action". When the piston 5 is further lowered, the crystal grain group is formed into one large lump solid product along the shape of the crystallization chamber 4. In this way, when the liquid is almost completely separated from the solid, the liquid phase pressure in the crystallization chamber 4 communicating with the drainage tank 6 under the atmospheric pressure is gradually lowered, so that the crystal surface is Partially melted, so-called "perspiration cleaning" is performed,
The bulk solid product is refined.

When the pressure of the drainage liquid discharged from the crystallization chamber 4 drops to a predetermined pressure, the lowering of the piston 5 is stopped,
When the high-pressure container 1 is also raised at the same time when the piston starts to move up, the solid product is placed on the lower lid 2 and the container 1
Taken from. This is taken out by a product take-out device (not shown), the high-pressure container 1 is lowered, and the lower lid 2
Then, the process returns to the raw material injection process, and the same process is repeated. Prior to the injection of the raw material, the residual liquid in the above-mentioned overflow pipe 15 is purged with a gas such as nitrogen gas which is inert to the product, and is prepared for full liquid detection at the time of injection in the next step. Keep it. By repeating the above steps, products are continuously produced.

[0009]

In the pressure crystallization step described above, it is necessary to maintain the pressure inside the pressure vessel 1 at a constant high pressure in order to separate the solid phase component and the liquid phase component. Needless to say, the pressure reducing function of the pressure reducing mechanism 10 must be properly exerted in order to discharge only the liquid component from the liquid phase discharge pipe 9 while maintaining this pressure.

By the way, when the liquid is discharged after being kept at the pressure for precipitating the crystals by pressure crystallization, if the speed at which the liquid passes through the filter in the pressure vessel 1: V _f is too large, the crystals are caught by the filter. It is empirically known that the recovery rate of crystals deteriorates because they are not collected and flow out together with the drainage as they are, and therefore appropriate control of V _f is necessary. In the case of a large pressure vessel, that is, when the volume of the stock solution to be supplied to the pressure vessel 1 at a time is large, the area of the filter provided in the pressure vessel 1 can be large, so that one nozzle as in the conventional case is used. However, the flow rate can be controlled.

However, when the device is downsized and the area of the filter in the pressure vessel cannot be made large, _Vf becomes too large with one nozzle and the flow rate must be further reduced. In order to reduce the flow rate, there is an attempt to adjust the flow rate by providing a throttle valve in front of the nozzle in the conventional device, but in reality, there is a problem that the adjustment cannot be sufficiently performed. If the nozzle diameter is reduced, it is possible to throttle the flow rate as specified, but the fine particles contained in the drainage cause nozzle clogging,
The current situation is that it cannot be actually operated. Further, in the case where one conventional nozzle is used, the flow coefficient K has the minimum limit, and therefore the drainage flow rate Q at the time of separation is also limited, and the crystallization yield is also a problem.

The present invention has been made in view of the above circumstances, and an object thereof is to overcome the above-mentioned problems of the conventional one and to solve the liquid phase in the solid-liquid separation step. It is an object of the present invention to provide a pressure crystallizer capable of lowering the minute discharge rate by using a reduced-pressure nozzle having a small discharge rate, thereby further increasing the product yield.

[0013]

In order to achieve the above object, the pressure crystallizer according to the present invention has the following constitution. That is, the apparatus according to claim 1 is connected to the high-pressure container via a high-pressure container, a mixture supply means for supplying the mixture into the container, a pressurizing means for pressurizing the mixture in the high-pressure container, and a decompression mechanism. In the pressure crystallizer having the liquid phase discharge pipe, the pressure reducing mechanism comprises a small diameter passage having a large fluid flow resistance on the upstream side, and a small diameter passage having a fluid flow resistance smaller than the small diameter passage on the downstream side. The pressure crystallizer is characterized in that a plurality of stepped nozzles included in 1 are connected in series to form a depressurizing nozzle whose flow rate can be changed rapidly and slowly alternately.

According to a second aspect of the present invention, some of the stepped nozzles of the plurality of stepped nozzles are different diameter stepped nozzles in which the diameter of the minute diameter passage is different from that of the other stepped nozzles. The pressure crystallizer according to claim 1. The apparatus of claim 3 is
3. The pressure crystallizer according to claim 1, wherein at least a part of the stepped nozzle is an eccentric stepped nozzle in which a small diameter passage and a small diameter passage are axially eccentric.

[0015]

The present invention is basically an invention of a pressure reducing mechanism capable of reducing the flow rate more than ever, even if the diameter of the nozzle is large to some extent.

That is, in general, the flow rate V passing through the nozzle is
Since V = a (2g / r) ΔP ^1/2 is expressed, the flow rate V _n when n nozzles with the same diameter are arranged in series is V ₁ when the flow rate when there is one nozzle is V _1. , V _n / V ₁ = 1 / n ^1/2
Becomes Therefore, it can be understood from this theory that the flow rate can be arbitrarily changed by adjusting the number of nozzles.

However, as shown in FIG. 5, by arranging in series n nozzles (referred to as straight nozzles) having the same diameter of the passage from the inlet to the outlet, the flow rate decreases due to an increase in flow resistance. Can be realized,
The decompression effect that doubles cannot be expected at all.

On the other hand, according to the present invention, a stepped nozzle having a small diameter passage and a small diameter passage in series from the inlet side to the outlet side is used as a unit member, and a plurality of these are connected in series. For example, as shown in FIG. 4, immediately after the flow rate of the liquid is once narrowed in the minute diameter passage, the liquid is decompressed by diffusion in the smaller diameter passage wider than that, and this flow rate control and pressure drop are alternately repeated in sequence. Therefore, it goes without saying that the flow rate is reduced and the pressure drop is performed reliably and effectively.

If a part of the stepped nozzles connected in series is a different diameter stepped nozzle, fine pressure reduction adjustment can be performed. or,
By using the eccentric stepped nozzle, the diffusion and the turbulent flow of the fluid occur in parallel in the small diameter passage interposed between the minute diameter passages that are eccentric to each other, so that the pressure reducing effect is further exerted.

Since the flow rate restriction and the pressure reduction are performed with high efficiency in this manner, it is possible to form a small pressure reduction mechanism.

[0021]

EXAMPLE The basic structure of a pressure crystallizer, which is an example according to the present invention, is the same as that shown in FIG.
Therefore, the structure and the function of the main part are the same as those described in the section of the prior art, and the description thereof is omitted here to avoid duplication, and the decompression mechanism 10, which is an important feature of the present invention, is described in detail below. I will describe.

2 to 3 are sectional front views of the decompression nozzle 20 in the decompression mechanism 10 according to each embodiment of the present invention. twenty one
A is a stepped nozzle which is a unit member for depressurization, and has a small diameter passage of, for example, a diameter of 0.3 mm from the end face on the inlet side, and a port of, for example, a diameter from the end face on the outlet side, in the central portion of a short cylindrical metal body. Small diameter passages with a diameter of φ1.5 mm are pierced by abutting each other, and at the boundary, there is an interface that is perpendicular to the axis of the passage.

A plurality of stepped nozzles 21A of the same size,
For example 10, after fitted into superposed in series within the nozzle case 23 in cylindrical in the same direction, the nozzle pressing also serving as the ends of the nozzle case 23, a lid provided with narrow passages through the central portion Consolidate each nozzle with 22 to ensure airtightness between the nozzles.
A decompression nozzle 20 as shown in FIG. 2 (A) is formed by connecting a pipe 24 to the outside end surface of each nozzle retainer 22 so that it can be held and is connected to the narrow passage.

Only one depressurizing nozzle 20 or a plurality of depressurizing nozzles 20 are connected in series, and the depressurizing mechanism 10 is provided in the middle of the liquid phase discharge pipe 9.
Is configured. Although not shown, the stepped nozzle 21A is shown in FIG.
In addition to the structure shown in (A), of course, a tapered stepped nozzle in which the boundary between the small diameter passage and the small diameter passage forms the interface of a tapered surface such as the peripheral surface of a truncated cone may be used.

In FIG. 2B, most of the 10 stepped nozzles are 8 stepped nozzles 21A having the same size, and the remaining 2 pieces are different in the diameter of the minute diameter passage. Diameter stepped nozzle
Except that 21B is a structural difference,
It has the same structure as in FIG. The different diameter stepped nozzle 21B may be of any size as long as the diameter of the minute diameter passage differs from the diameter of the stepped nozzle 21A. By using the different-diameter stepped nozzle 21B in this way, it is possible to finely adjust the reduced pressure value.

FIG. 3A shows an example in which three depressurizing nozzles 20 shown in FIGS. 2A and 2B are connected in series to form the depressurizing mechanism 10. In addition, it is used when increasing the reduced pressure.

FIG. 3B is different from the above-mentioned examples in that an eccentric stepped nozzle 21C is used as a pressure reducing nozzle, and the other structures are the same. This eccentric stepped nozzle
In 21C, a small-diameter passage and a small-diameter passage are axially eccentric and are provided in series. Preferably, for convenience of connection, the small-diameter passage is provided in the center of the main body, and the small-diameter passage is provided with axial eccentricity. The one given is good. Such a decompression nozzle can enhance the decompression effect as a result of not only the diffusion of the liquid in the small diameter passage but also a large turbulent flow.

A decompression mechanism constructed by interposing one decompression nozzle 20 (the number of stepped nozzles 21A: 10) shown in FIG. 2 (A).
In 10, when it was pushed in with a pressure of 2,000 kg / cm ² ,
The outlet pressure became atmospheric pressure.

[0029]

EFFECTS OF THE INVENTION The pressure crystallizer according to the present invention has the structure described above and functions, and by using a pressure reducing nozzle in which a plurality of stepped nozzles are connected in series as the pressure reducing mechanism 10, The effect of reducing the flow rate and the pressure is extremely large, and there is an advantage that it can be realized in a small size. Further, the present invention has an effect that the filtration rate can be adjusted easily and surely by the difference in the number of the stepped nozzles and the diameter, and that the filtration rate can be sufficiently slowed to efficiently realize the crystal precipitation. .

[Brief description of drawings]

FIG. 1 is a diagram showing a process flow of a pressure crystallizer and a concept of the apparatus.

FIG. 2 is a cross-sectional front view of a pressure reducing nozzle in the pressure reducing mechanism according to the embodiment of the present invention.

FIG. 3 is a cross-sectional front view of a decompression nozzle in the decompression mechanism according to the embodiment of the present invention.

FIG. 4 is a cross-sectional front view of a pressure reducing nozzle in the pressure reducing mechanism according to the embodiment of the present invention.

FIG. 5 is a cross-sectional front view of a pressure reducing nozzle in the pressure reducing mechanism according to the embodiment of the present invention.

[Explanation of symbols]

1--High-pressure container 3--Hydraulic unit 4 --- Crystallization chamber 5--Piston 8--Raw material supply pump 9--Liquid phase discharge pipe 10--Decompression mechanism 20--Decompression nozzle 21A--
Stepped Nozzle 21B--Different Diameter Stepped Nozzle 21C--Eccentric Stepped Nozzle

Claims (3)

[Claims] 1. A liquid phase connected to a high pressure vessel, a mixture supply means for supplying a mixture into the vessel, a pressurizing means for pressurizing the mixture in the high pressure vessel, and a depressurization mechanism. In a pressure crystallizer having a discharge pipe, the pressure reducing mechanism, a small diameter passage having a large fluid flow resistance upstream side,
A plurality of stepped nozzles having a small-diameter passage having a smaller fluid flow resistance on the downstream side than the small-diameter passage are connected in series to form a decompression nozzle capable of changing the flow velocity rapidly and slowly alternately. Characteristic pressure crystallizer. 2. The stepped nozzle according to claim 1, wherein some of the stepped nozzles among the plurality of stepped nozzles are different-diameter stepped nozzles in which the diameters of the minute diameter passages are different from those of the other stepped nozzles. Pressure crystallizer. 3. The pressure crystallizer according to claim 1, wherein at least a part of the stepped nozzle is an eccentric stepped nozzle in which a small diameter passage and a small diameter passage are axially eccentric.