JPS63218204A - Method and device for pressure cooling crystallization - Google Patents

Abstract

PURPOSE:To separate a specified component from a raw mixture contg. the specified component with a relatively low operating pressure and with high heat efficiency, by carrying out a cooling stage wherein the crystals of the specified component are rapidly increased while the mixture is transported at high speed under high-pressure conditions. CONSTITUTION:The raw mixture contg. a specified component is cooled to the vicinity of ordinary temp. in a precooling vessel 1. The mixture is then pressurized to a specified pressure by high-pressure pumps 8a and 8b, supplied to a raw material supplying pipeline L1, further, cooled by a cooling mechanism 9, and sent into a high-pressure chamber 4. After the opening of a mother liquor discharge nozzle N is adjusted, the mother liquor is passed through a screen, separated, and discharged. When the pressure in the high-pressure chamber 4 is then decreased to some extent, the piston 5 is operated to carry out compression, hence the mother liquor adhered to the surface of the crystal in the high- pressure chamber 4 is squeezed out along with the specified component slightly melted from the surface layer due to the pressure decrease, and only the high- purity specified component is left in the high-pressure chamber 4.

Description

Detailed Description of the Invention [Industrial Field of Application] The present invention provides an improved pressurization method that enables crystallization and separation of a specific component from a raw material mixture containing the specific component at a relatively low operating pressure and with high thermal efficiency. The present invention relates to a cooling crystallization method and a pressurized cooling crystallization apparatus that is advantageously used in this method.

[Conventional method] The pressurized cooling crystallization method is a method in which a raw material consisting of a liquid phase or slurry containing multiple components is generally pre-cooled and then introduced into a high-pressure container, with the mother liquor discharge pipe closed. This is a method of applying high pressure (for example, high pressure exceeding 1000 atmospheres) to promote the crystallization of a specific component, and through this operation, a solid-liquid mixed state consisting of crystals of the specific component and residual liquid (mother liquor) is obtained. . At that point, the mother liquor discharge pipe is unblocked, piston pressure is applied to the above-mentioned solid-liquid coexistence state, the mother liquor is discharged out of the system via the filter, and the remaining solid phase is squeezed to further separate the solid and liquid. By discharging the gas, high-purity specific components can be recovered.

For example, FIG. 3 is a conceptual diagram showing a conventional pressure crystallizer, in which the raw material mixture A is cooled to an appropriate temperature in the pre-cooling tank 1, and then passed from the slurry pump 2 to the raw material supply pipe L! It is fed into the high pressure chamber 4 of the pressure crystallizer 3 through the pressure crystallizer 3. After driving the piston 5 to pressurize the raw material in the high pressure chamber 4 and increase or generate crystals of a specific component in the raw material, the liquid phase component (mother liquor) is squeezed and discharged from the screen through the mother liquor discharge pipe L2. After that, the crystals of the specific component remaining in the high pressure chamber 4 are recovered. In the figure, V, V2 are on-off valves, N is a discharge nozzle, 6 is a drain tank, and 7 is a pressurizing unit, respectively.

The steps of the pressure crystallization method described above are as follows.

! Step I: Close the on-off valve v2 and open the on-off valve v1 to supply the raw material mixture into the high pressure chamber 4, I: Close the on-off valve vI, actuate the piston 5 to apply high pressure to the raw material mixture, and specify Step of increasing or generating crystals of the components, III: Opening the on-off valve ■2 and discharging the mother liquor in the high pressure chamber 4 via the screen, the mother liquor discharge pipe L2 and the discharge nozzle, ■: Activating the piston 5. V: Step of opening the high pressure chamber 4 and taking out crystals of a specific component.

After the above step V is completed, the process returns to step I, and by repeating this operation, the specific component is continuously separated and recovered. FIG. 4 conceptually shows the change in operating pressure over time during the operation, and FIG. 5 similarly shows the relationship between temperature and pressure during the operation.

[Problems to be solved by the invention] In Fig. 3, the straight line W is the solid-liquid equilibrium line of a specific component (pure substance), the straight line ksx is the solid-liquid equilibrium line of the raw material mixture, and Y is the mother liquor separated by high-pressure crystallization. The isoconcentration line Z indicates the solid-liquid equilibrium line of the eutectic mixture, and high-pressure crystallization separation is performed along the thick solid arrow.

That is, when the raw material mixture is pre-cooled to point A and then pressurized,
The pressure increases rapidly with almost no temperature rise until it reaches point B (the point of intersection with straight line , a considerable temperature rise can be seen as the pressure increases. In this example, the raw material mixture is pressurized to a pressure P to generate or increase crystals of a specific component, and then the uncrystallized mother liquor is filtered and discharged to recover a highly pure specific component. In this case, the temperature rises to T due to heat generation accompanying the crystallization of a specific component. In the conventional example, after this state is obtained, the on-off valve V2 (Fig. 3) is opened to discharge and remove the mother liquor.
The mother liquor is further squeezed to remove the mother liquor more completely, but if the operating pressure is lower than the straight line W, even the specific components that have been taken pains to crystallize will be melted and discharged, resulting in loss. Therefore, by adjusting the opening degree of the discharge nozzle N or cooling it, the relationship between operating pressure and temperature is controlled so as not to fall below the straight line W.

As can be easily understood from this figure, the pressure needed to efficiently promote the crystallization of a specific component increases rapidly as the raw material temperature increases, but in the pressure crystallization process, as described above, As the temperature progresses, the temperature of the raw material increases due to condensation, so the operating pressure must be increased accordingly. Not only must the pressure-resistant design strength of the fruiting equipment and piping lines be extremely high, but the pressurizing performance of the pressurizing unit must also be extremely high.
Equipment costs are rising. Moreover, in this method, the pressure difference between the pressure during crystallization separation and the pressure during pressure release (normal pressure) is extremely large, so a large amount of crystals of specific substances are melted in the final compression process, resulting in a decrease in yield. There is also the problem of doing so.

The inventors of the present invention have devised a method as shown by the broken line arrow in FIG. 5 as a means to improve these problems. In other words, the raw material mixture is predictively cooled to a lower temperature than in the conventional method.
This is a method in which the temperature is lowered to a certain point, and then pressure crystallization is performed.With this method, the temperature after pressure crystallization (To) can be kept low by the same amount as the pressure starting temperature is lowered. , as shown at point 0, the same crystallization efficiency can be obtained at a pressure P° that is considerably lower than the previous crystallization operating pressure P.

Moreover, since the pressure difference between the pressure during crystallization separation and the pressure during pressure release can be suppressed to a small level, a decrease in the yield of specific component crystals can also be suppressed.

However, in this method, the raw material mixture is moved from point A to A°
A large cooling device is required to cool the product to a certain point, and in particular, when attempting to cool the product below room temperature, a dedicated refrigeration device is required in addition to the normal water-cooled pre-cooler, which significantly increases the initial cost and running cost. be done. Moreover, if the amount of crystals in the raw material mixture increases too much during this cooling process, it may cause clogging in the piping 1 leading to the supply to the high pressure chamber 4, the on-off valve Vlx, the slurry pump 2, etc. , and may even become inoperable.

The present invention has been made in view of these circumstances, and its purpose is to reduce the crystallization operation pressure by lowering the crystallization operation temperature, and to reduce the accompanying burden on refrigeration equipment, etc. It is an object of the present invention to provide a pressurized cooling crystallization method that does not cause pipe line blockage, etc., and an apparatus that can be advantageously applied to carry out such a crystallization method.

[Means for solving the problems] The structure of the crystallization method of the present invention that can achieve the above object is as follows: I: Pressurizing the temperature-controlled raw material mixture; By cooling the mixture while passing it through a high-pressure pipe maintained at a lower temperature than the raw material temperature after pressurization, crystals of a specific component are generated or increased, and the crystals are injected into a solid-liquid separator, and then solid-liquid A step of separating and discharging the mother liquor from the coexisting raw material mixture via a filtration mechanism, III: Stopping the supply of raw materials to the solid-liquid separator and discharging the residual mother liquor at a lower pressure than in the mother liquor separation/discharge step. The apparatus of the present invention is an apparatus for pressure-cooling crystallization of a specific component from a raw material mixture containing the specific component, and includes a step of controlling the temperature of the raw material mixture. mechanism, a pressurized supply mechanism for the raw material mixture, high-pressure piping for conveying the pressurized raw material mixture, a solid-liquid separation device equipped with a filtration separation mechanism, and a mother liquor discharge piping equipped with a flow rate adjustment mechanism or a pressure adjustment mechanism. The gist lies in the fact that it is prepared.

[Operations and Examples] As explained in FIG. We thought that if we first pressurized the water to raise its temperature and then cooled it down, there would be a considerable temperature difference between it and the normal water temperature, and that efficient cooling could be achieved even with water cooling.

That is, it is also economical since there is no need to use a special refrigeration device. To explain such an operating procedure according to Fig. 5, as shown by the broken line arrow in Fig. 5, for example, in order to cool a raw material mixture near room temperature to below room temperature (for example, below about θ°C), the target It is necessary to use a low-temperature refrigerant depending on the temperature, and the use of a freezing device is essential. However, if a raw material mixture that has been heated to about 50°C or higher by pressurization is to be cooled down to around room temperature, it is necessary to use a refrigerant at room temperature. It should be possible to fully achieve the purpose of cooling by using industrial water as is.

The present inventors took advantage of this idea and devised a method in which the raw material is first pressurized and then cooled once the temperature of the raw material has risen to a certain extent. In other words, the solid line arrows in Figure 1 indicate pressure and temperature changes when this method is adopted [the thin chain line arrows correspond to the thick solid line arrows (conventional method) in Figure 5], and the raw material mixture A When pressurized from point B, the pressure and temperature increase toward point 0, but at point C' in the middle, that is, the pressure reaches p' and the temperature reaches T1 point. If the pressure increase is stopped, the temperature is cooled to point D, and the mother liquor is separated and squeezed out after crystallization at this point, the conventional method
It is possible to obtain the same crystallization and separation effect as crystallization and separation/squeezing of the mother liquor at the point, and in addition, there are many advantages such as lower operating pressure and temperature, reduced pressure drop during pressure reduction, and improved cooling efficiency. You can enjoy the effects of However, being able to cool the entire crystallizer under pressure places a heavy burden on the equipment, and there is a risk that pipe clogging will occur if a large amount of crystals have precipitated due to pressurization and cooling and is then fed into the high-pressure chamber. comes out.

From this point of view, in the present invention, as described above, first [I]
Pressurize the temperature-controlled raw material mixture.

At this stage, a part of the specific component in the raw material mixture may or may not be crystallized, and may be in a supersaturated or unsaturated state.
By cooling the pressurized raw material mixture while passing it through a high-pressure pipe maintained at a temperature lower than the temperature of the raw material after pressurization, crystals of a specific component are generated or increased, and the solid-liquid separation device ( That is, a method is adopted in which the mother liquor is injected into a high-pressure chamber and the mother liquor is subsequently separated and compressed and filtered in the same manner as in the conventional example. In other words, the present invention employs a method in which the cooling process in which crystals of a specific component rapidly increase is carried out under high pressure and high-speed transport, resulting in finer crystals and improved fluidity compared to when crystallization is performed in a static state. It is possible to maintain a good slurry state and prevent pipe clogging as much as possible. Moreover, since high-pressure piping is traditionally configured to have a smaller diameter than normal-pressure piping, indirect cooling using cooling water or the like can be performed efficiently. In this way, the objectives of ■reducing operating pressure and temperature, ■preventing pressure drop and the resulting decrease in yield, and ■simplifying cooling equipment and increasing cooling efficiency can be achieved all at once without causing problems with pipe clogging. It became.

FIG. 2 is a schematic flow diagram illustrating an apparatus used in carrying out the above method, and the structure of the crystallizer main body 3 and subsequent parts is substantially the same as the conventional example shown in FIG. Duplicate explanations will be omitted by assigning the same reference numerals to the same parts. As is clear from the illustrated example, the main feature of the present invention is the process up to supplying the raw material mixture into the high pressure chamber 4 of the crystallizer main body 3, and the raw material mixture A is first heated in the preliminary cooling tank 1. After being cooled down to around room temperature by a water cooling mechanism (not shown) or the like, the material is raised to a predetermined pressure by high-pressure pumps 8a and 8b, and is fed through the raw material supply pipe in one direction. The pressurized feeding process up to this point is from A to B- in Fig. 1.
This corresponds to step C'. The plan view shows an example in which two piston-type high-pressure pumps are installed in parallel and can be operated continuously by switching operation, but three or more piston-type high-pressure pumps can be installed in parallel, including a backup pump, or one high-pressure pump can be operated intermittently. It is also possible to adopt a configuration in which the pressure is fed, and it is also of course possible to employ other high-pressure feeding mechanisms such as a gear pump type. These high pressure pumps 8
The raw material supply pipe L1 after a and 8b has a pressure-resistant structure, and a cooling mechanism 9 is attached to the pipe L1 located immediately before the crystallizer main body 3. Cooling of the mixture takes place. This cooling step corresponds to the step C→D in FIG. It is of course effective to use a bellows tube or a finned tube as the raw material supply conduit through which the cooling is performed to improve cooling efficiency. It is also possible to use ammonia gas etc. as a refrigerant, but
In view of the purpose of the present invention, which is to simplify the cooling equipment, cooling water is most advantageous, and since the raw material mixture flowing through the supply pipe in the present invention is at a considerably high temperature due to pressure increase as described above, it is not necessary to use ordinary industrial water. etc. can also be sufficiently cooled. Of course, it is also possible to use ice water or the like if necessary.

The raw material mixture pressurized and cooled in this way is
The mother liquor is sent from I to the high pressure chamber 4, and then the on-off valve V is closed, the on-off valve 2 is opened, and after adjusting the opening of the discharge nozzle, the mother liquor is separated and discharged through a screen (not shown). After that, when the pressure in the high pressure chamber 4 becomes slightly lower than the above pressure, the piston 5 is operated to perform compression.
The mother liquor adhering to the surface of the crystal in the high pressure chamber 4 is squeezed out along with a slight amount of the melted specific component from the surface layer due to the pressure drop, leaving only highly purified crystals of the specific component in the high pressure chamber 4. Therefore, the high-pressure chamber 4 may then be opened to take out the specific component in the form of a cake, or the high-pressure chamber 4 may be depressurized and heated to once melt the crystals of the specific component, and then taken out through a separately provided discharge pipe.

As can be easily understood from the above explanation, the present invention basically uses the high pressure pumps 8a and 8b to secure the crystallization operating pressure, and the cooling mechanism 9 to ensure the crystallization operating temperature. No pressure rise or temperature fall occurs within the analyzer main body 3, and the piston 5 is used only during compression. Therefore, when the content of a specific component in the raw material mixture is low (the amount of crystallization is relatively small relative to the mother liquor), the raw material mixture is cooled under pressure and fed into the high pressure chamber 4, and the mother liquor is continuously passed through a filter. If the specific component crystals are discharged and the compression separation step is started when a certain amount of specific component crystals have accumulated in the high pressure chamber 4, the opening degree for extracting the specific component crystals (i.e., the number of times the high pressure chamber 4 is opened) can be changed.
This is preferable because it can reduce the amount of water and improve both productivity and operability. In this case, a pressure gauge P1 is provided on the raw material inlet side of the high pressure chamber 4, and a pressure gauge P2 is provided on the mother liquor outlet side, and these Ps and Pz are connected to a differential pressure sensor Q+.
If the differential pressure sensor Q+ detects that a predetermined amount of crystals have accumulated in the high pressure chamber 4, an automatic control circuit can be constructed to start compression (that is, actuation of the piston 5). , it is possible to accurately control the setting of the compression start time according to the accumulation of crystals.

In addition, if the mother liquor discharge side pipe is depressurized all at once to atmospheric pressure in the final compression separation step, the influence of this depressurization extends to the inside of the high pressure chamber 4, increasing the amount of melted specific component crystals and decreasing the recovery rate. Although there is a risk, if measures such as arranging a plurality of pressure relief nozzles in series on the mother liquor discharge side line are taken to reduce the pressure on the mother liquor discharge side continuously or stepwise in the compression separation process, It is possible to suppress the melting and pressing loss of specific component crystals to the necessary minimum.

By the way, in the present invention, as mentioned above, a method of cooling in a high-pressure fluidized state is adopted, and pipe clogging due to crystallized substances is unlikely to occur, but if overpressure or supercooling state occurs during operation, crystallization may occur. Since there is a possibility that pipe clogging may occur due to a sudden increase in waste, it is best to take measures to anticipate such a situation. From this point of view, in the example shown in FIG. 2, a mechanism that can automatically detect clogging of the raw material supply line is also added. That is, the high pressure pump 8a.

Pressure gauges Pa and Pb are provided in the raw material discharge line of 8b, respectively, and the pressure gauge PI provided in the raw material inlet line to the high pressure chamber 4 is utilized to measure these Pa.

Pb and Pl are connected to a differential pressure sensor Q2, and the differential pressure between them is constantly detected. If clogging occurs in the raw material supply pipe LI between Pa or pb and PL, the differential pressure sensor Q2
Since the differential pressure detected by this increases rapidly, by detecting this differential pressure, it is possible to immediately know if the pipe is clogged.

Therefore, when such a phenomenon occurs, the pressure pump 8a,
8b is stopped to release the pressure inside the raw material supply pipe L1, or hot water or the like is supplied to the inside of the cooling mechanism 9 to heat the inside of the pipe L1 and melt the crystals in the pipe L1. If you let me,
Pipe clogging can be cleared immediately.

[Effects of the Invention] The present invention is configured as described above, and its effects are summarized as follows.

■Since we use a method that cools the raw material mixture while it is pressurized and heated, it can be cooled efficiently even with cooling water at room temperature, and there is no need for special refrigeration equipment, which reduces running costs. Can be reduced.

■Since pressure crystallization can be performed at a relatively low temperature, there is no need to increase the pressure excessively, and the overall pressure resistance of the equipment can be designed to be low, reducing equipment costs and improving operability and safety. Can be done.

■It is possible to reduce the pressure drop during pressure cooling crystallization and depressurization extraction, and the melt loss of specific components can be suppressed to the necessary minimum.

(2) The features of the present invention shown in (1) to (4) above are most effectively exhibited in the pressure-cooling crystallization separation of substances whose temperature increases due to pressure increase.

[Brief explanation of the drawing]

Fig. 1 is an explanatory diagram showing the transition of pressure and temperature when the method of the present invention is adopted, Fig. 2 is a schematic flow diagram showing an embodiment of the present invention, Fig. 3 is a conceptual diagram showing the conventional method, and Fig. 4 The figure is a graph showing changes in pressure over time when the conventional method is employed, and FIG. 5 is an explanatory diagram showing changes in pressure and temperature when the conventional method and the improved method are employed. 1: Pre-cooling tank 2 Nis slurry pump 3: Pressure crystallizer main body 4: High pressure chamber 5: Piston 6: Mother liquor tank 7: Pressurization units 8a, 8b: Pressure pump

Claims (6)

[Claims] (1) I: Pressurizing the temperature-controlled raw material mixture; II: Cooling the pressurized raw material mixture while passing it through a high-pressure pipe maintained at a lower temperature than the raw material temperature after pressurization. A step in which crystals of a specific component are generated or increased and injected into a solid-liquid separator, and then the mother liquor is separated and discharged from the raw material mixture in a solid-liquid coexistence state via a filtration mechanism. III: Solid-liquid separator A method for pressurized cooling crystallization of a specific substance, comprising the steps of: stopping the supply of raw materials to the mother liquor, and discharging the residual mother liquor at a pressure lower than that in the mother liquor separation/discharge step. (2) The pressurized cooling crystallization method according to claim 1, wherein pressurization of the raw material mixture, injection into a solid-liquid separator, and separation of the mother liquor by the solid-liquid separator are continuously carried out. (3) In the step III, the crystals in the solid-liquid separator are squeezed under pressure while the mother liquor is discharged while being continuously or stepwise reduced in pressure. Pressure cooling crystallization method. (4) An apparatus for pressurizing and cooling crystallizing a specific component from a raw material mixture containing a specific component, which includes a temperature adjustment mechanism for the raw material mixture, a pressurized supply mechanism for the raw material mixture, and a mechanism for conveying the pressurized raw material mixture. A pressurized cooling crystallizer comprising a high-pressure pipe, a solid-liquid separator equipped with a filtration separation mechanism, and a mother liquor discharge pipe equipped with a flow rate adjustment mechanism or a pressure adjustment mechanism. (5) A differential pressure sensor is provided to detect the differential pressure between the raw material inlet side pressure and the mother liquor outlet side pressure of the solid-liquid separator, and when the differential pressure detected by the sensor reaches a predetermined value, the solid-liquid 5. The pressurized cooling crystallizer according to claim 4, further comprising a mechanism for starting compression of the raw material in the separator. (6) Equipped with a pressure sensor that detects the differential pressure between the outlet pressure of the pressure increase mechanism and the raw material inlet pressure of the solid-liquid separator, and detects clogging in the high-pressure pipe based on the differential pressure detected by the sensor. A pressurized cooling crystallizer according to claim 4 or 5, which is adapted to perform the following steps.