JPS6112724B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a series of processes for separating, purifying and extracting substances under high pressure, and in particular, crystallizing specific components under high pressure, separating mother liquor by squeezing, and extracting solids. It is related to.

A method of crystallizing and separating one or more specific components from a multicomponent liquid phase or solid-liquid coexistence phase of two or more components is widely used as a fractional crystallization method. However, the conventional fractional crystallization method uses temperature as a parameter and performs crystallization separation by cooling a mixed system, and technology that uses pressure as a parameter has a short history, and there are many fields whose actual nature is still unknown.

FIG. 1A is a transformation diagram for explaining the conventional crystallization method using temperature as a parameter. For example, point A [temperature: To, composition: X ₁₀ , X ₂₀ (X ₁₀ = 1-X ₂₀ )] When the _mixture at is cooled _, high-purity crystals _{of component} Xe), _X2
(X ₂ =Xe)] to a temperature as close as possible to sufficiently increase the amount of solid phase, and then separate the solid and liquid. On the other hand, Figure 1B shows the corresponding transformation diagram when pressure is introduced as a parameter.
The straight lines indicated _by X ₂ = 0, X _{2 =} X ₂₀ , and _{X 2 =} Each solid-liquid transformation line when ₂ is a eutectic composition,
A mixture of each composition has a solid phase on the high pressure side or low temperature side of each solid-liquid transformation line.

Now, the case where fractional crystallization is carried out according to FIG. 1B will be explained as follows. First, when the mixture at point A is pressurized isothermally, it reaches the line of X ₂ = X ₂₀ (transformation point) at point A', and the specific component X ₁
begins to crystallize as a solid phase. If the isothermal pressurization is continued, the transformation line of the eutectic point composition, X ₂ =Xe, is reached (point F), so it is sufficient to separate the solid and liquid at a position as close to point F as possible. This operation should be called an isothermal pressure crystallization method, and although it can be explained as a reference pattern, in reality, it is extremely difficult to implement for the following reasons.

Generally, when a substance is pressurized, the amount of heat generated is extremely large. For example, pure benzene (liquid phase) at 27℃,
In order to pressurize to the transformation pressure (770 atm) at that temperature and start solidifying benzene,
Heat radiation of 8 cal/g is required, and further heat radiation of approximately 30 cal/g is required to solidify the entire amount under this pressure.

Therefore, in order to maintain isothermal conditions, the heat released must be absorbed by using a large heat exchanger or by long-term heat exchange (slow pressurization rate).

However, it is technically difficult to incorporate a heat exchanger into a high-pressure device, and even if it were possible to do so, it would be an obstacle during solid-liquid separation. Also, a low pressure increase rate is industrially disadvantageous. Furthermore, since high-pressure containers are generally thick-walled, the thermal efficiency of methods for dissipating heat to the outside of the container (or cooling from the outer surface of the container) is very poor.

Furthermore, since the heat exchange method essentially produces a temperature distribution, the greatest advantage (uniformity within the system) of pressure crystallization is lost.

These difficulties become more noticeable as the throughput increases, but similar problems also occur when temperature control is not performed during pressure increase and cooling is performed after reaching a predetermined pressure. For example, in Fig. 1B, if the mixture at point A is pressurized without temperature control, the temperature rises due to the heat of compression, and reaches the line X ₂ = X ₂₀ at point A'_' , causing crystallization of the specific component Separation begins. If the pressure is continued, the amount of crystallization of _component Rise along the chain line.
Therefore, when the pressure increase is stopped at point G' and cooling is started, the temperature decreases along the thin solid line G'→F,
Ultimately, crystallization is completed at or near point F, but the technical difficulty and uneconomical nature of the cooling step, as well as the heterogeneity within the system due to temperature differences, are as described above, so the essential point is I can't say it's a perfect solution.

As described above, crystallization methods for substances that apply high pressure involve extremely complex problems compared to conventional crystallization methods that simply use temperature as a parameter. Furthermore, the following difficulties are encountered in separating the crystals thus crystallized from the mother liquor and taking them out into atmospheric pressure.

As solid-liquid separation means, the compression separation method (filter press method), general filtration method, centrifugation, etc. are known, and although these can be used as appropriate even under high pressure, the compression separation method is considered to be the most preferable method. It is being However, in compression separation under high pressure, the following complicated aspects were observed.

FIGS. 2A, B, and C are schematic cross-sectional views for explaining the squeezing situation under high pressure. First, FIG. 2A shows a state in which a solid phase S is uniformly dispersed in a liquid phase L having a very low viscosity. Of course, the inside of the high-pressure container 1 is maintained at high pressure, and 2 is a piston, 3 is a filter, and 4 is a packing. If the piston 2 is lowered at this stage, the liquid phase L in the system will pass through the filter 3.
It is squeezed out of the system and separated. At the beginning of the squeezing operation, the pressure inside the system P ₁ and the pressure at the back of the filter 3
The difference in P ₂ is very small and is due to the speed at which the liquid phase L passes through the filter 3.

By the time the piston 2 gradually descends and reaches the state shown in FIG. 2B, a considerable amount of the liquid phase L has flowed out. Therefore, a considerable amount of the solid phase S accumulates on the filter 3, and the resistance to the outflow of the liquid phase L increases, causing _P1 and
The difference in P ₂ becomes larger. However, this stage is substantially the same as the commonly-called filtration process, and the filter 3
The interstices between grains in the filter cake 5 of solid phase rich accumulated on top are still quite wide.

When the piston 2 is further lowered to reach Figure 2C, a filter cake 5 is formed throughout the system, and _P1 and
The pressure difference of P ₂ becomes even larger, and the cake 5 near the filter 3 becomes even more dense. Therefore, in order to further compress and separate the liquid phase L remaining in the system, the difference between the piston pressure P ₃ per unit area and the filter back pressure P ₂ is further increased, and the crystal grains themselves are compressed and separated. It is necessary to collapse the voids between crystal grains.

This type of solid-liquid compression separation method is generally called the filter press method and is widely used industrially, but even if a compression pressure of more than 100 kg/cm ² is applied, sufficient dehydration or liquid removal cannot be achieved. It is said that Moreover, in the case of coexistence compression separation of a solid phase of a specific substance and a mother liquor of a mixture containing the specific substance, such as the fractional crystallization method, if the mother liquor remains, the higher the concentration of other components in the mother liquor, the lower the purity achieved in the product solid. This tendency is particularly strong in fine-grained solids. Therefore, when applying the compression method to the crystallization separation method under high pressure that the present inventors are dealing with, it is necessary to apply the filter press method under normal pressure as described above as is.
There are various problems associated with this method, such as a decrease in separation performance.

It has also been found that even if compression separation can be carried out satisfactorily, there are still some problems when taking out this solid into atmospheric pressure.

For example, FIG. 3 is a solid-liquid phase diagram of a three-component simple eutectic mixture, and the lines and have the same meanings as in FIG. 1B. The points M, M', and M'' indicate these solid-liquid coexistence points.

First, it is assumed that the compression separation of solid and liquid is completed at point M'. When the separated solid is depressurized, it reaches the N′ point. Since the solid expands during this pressure reduction process, there is some cooling due to the heat of expansion, but it does not expand as much as a liquid and its influence is small, so it will be ignored for convenience.
As the pressure continues to decrease, the pressure decreases along the transformation line toward point E, but at the same time the crystals begin to melt. At this stage, latent heat due to melting of the crystal and internal energy decrease due to expansion of the melt occur, and the temperature also drops rapidly. When the entire amount melts at point E,
Since the rest is only a factor associated with the expansion of the liquid, the amount of temperature drop is reduced. Note that Tm is the melting point of pure component X ₁ under atmospheric pressure.

On the other hand, when solid-liquid separation is performed at point M or M'', even if this solid phase is released into atmospheric pressure, the entire amount will not melt.For example, if depressurization is started from point M, then point N Melting begins at this point, and the pressure and temperature decrease in the same way as the melting occurs, but the melting point Tm is quickly reached and the melting does not proceed any further.If the solid-liquid separation at the M point is insufficient, crystallization The effect of some melting as the pressure decreases appears as latent heat, and the amount of temperature decrease increases, reaching point C.The pressure and temperature decrease further, but since impurities are mixed in,
The progress of melting stops when a temperature lower than the melting point Tm is reached. If compression separation at point M is still insufficient, point D is reached with some melting without reaching the line. In this way, when starting from point M, only a portion of the solid phase melts, and its purity is extremely low. Furthermore, this tendency becomes even more pronounced when starting from point M''.

In general, the temperature drop that accompanies pressure reduction can take various forms, but the amount of temperature drop when pressure is reduced adiabatically is very large. For example, when melting ordinary organic substances, the temperature decreases as much as 100 to 150°C, so in the case of Figure 3, the distance between N' and E is 100°C.
Total melting is possible only when there is a temperature difference of ~150°C. In addition, the temperature dependence (slope of the line) of the transformation pressure in many organic materials is 30 to 60 kg/
cm ² , so if the temperature difference between N' and E is 100℃, the pressure difference between N' and E is 3000 to 6000 kg/
Must be cm ² . Moreover, the pressure when actually performing solid-liquid separation is often several hundred to several thousand atmospheres higher than this, and in the end, in order to melt the entire amount of solid only by depressurization, it is necessary to reach the M' point. The pressure must be extremely high.

However, it has the disadvantage of requiring special pressure equipment, so either a heat exchanger is placed inside a high pressure vessel, or
It is not inconceivable to use the heating device of the high-pressure vessel itself. However, in the former case, compression separation in a high-pressure vessel becomes difficult, and in the latter case, thermal efficiency is poor.

As described in detail above, there are difficult problems in any one of the pressure crystallization step, the compression separation step, and the specific component extraction step. The present invention has been made in view of these circumstances, and it is an object of the present invention to provide a method for solving the above problems all at once.

Therefore, the structure of the present invention is that in the step of crystallizing one or more specific components from a mixture of two or more components, the temperature of the mixture is controlled under atmospheric pressure or under low pressure. After applying pressure to a temperature at which the specific component is likely to crystallize, the mixture is substantially adiabatically pressurized to solidify a portion of the specific component or to solidify by increasing the solid phase. The key point is to create a liquid coexistence state, and in the solid-liquid compression separation process, the pressure of the liquid phase to be separated after passing through the filter is lower than the pressure at the time when the filtration resistance begins to increase. The gist lies in squeezing the solid phase, or
Even if this pressure temporarily increases after the start of separation, the gist is to carry out solid-liquid separation while keeping this pressure lower than the previous pressure at least after the start of compression separation. Furthermore, in the process of extracting specific components, the pressure on the solid phase is returned to atmospheric pressure or a pressure close to it to melt a portion of the solid phase, and at the same time the high pressure container is opened and the solid is extracted into atmospheric pressure. There is a gist. These are hereinafter referred to as an adiabatic pressurization step, a compression separation step, and a solid extraction step, but the present invention also includes a case where the solid-liquid coexistence mixture is locally cooled to proceed with solidification immediately after the adiabatic pressurization step ends.

The present invention will be explained separately for each step below.

(1) Adiabatic pressurization process This process is further divided into a first process of temperature adjustment and a second process of adiabatic pressurization.
I will explain the process first.

First, the substantial adiabatic pressurization referred to in the second step means that the amount of heat exchanged between the mixture and attached equipment such as the high-pressure container, piping, pressurizing equipment, pressure gauges, thermometers, squeezing equipment, and pipe joints is It means pressurized operation under conditions that can be practically or industrially ignored. Although there are no particular restrictions on the specific means for achieving such adiabatic pressurization, the following two methods are exemplified as typical methods. The first method is to reduce the amount of heat transfer by forming a heat insulating layer on all or part of the high-pressure container, piping, pressurizing equipment, and attached equipment, and the second method is to increase the pressure of the mixture as soon as possible. In this method, crystallization is completed without creating a temperature gradient in the system. Of course, if these methods are used together, adiabatic pressurization can be carried out even more conveniently, but the point is that the temperature increase due to pressurization is sealed within the system and the system is made uniform. Therefore, to explain the case in Figure 1 B, the mixture that has been pressurized from A to A'' is pressurized as it is to point G, and the temperature is allowed to rise to complete crystallization. In this case, the container temperature (including piping temperature, etc.) may be pre-adjusted to the temperature reached after pressurization (temperature at point G), but if the function of the heat insulating layer is sufficiently effective or As long as high-speed adiabatic pressurization is possible, most of the heat exchange with the mixture can be avoided, so in the present invention, there are few restrictions on the container temperature, etc.

However, the temperature of the mixture filled into a high-pressure container or the like may require some degree of control, and for this reason the first step is carried out in the present invention.

That is, in the above explanation, the mixture at point A, which is the temperature T ₀ , was pressurized, but as shown in FIG. 1B, the first crystallization occurs only when the pressure is applied from A to A''. Therefore, the temperature at point A'' has become even higher than _T0 , and if we look at this in relation to A in Figure 1, we can see that the temperature has moved to the side where crystallization of the specific component _X1 is less likely to occur. , and it is not a useful purpose. Therefore, in cases where the mixture is mostly in a liquid phase or entirely in a liquid phase at room temperature and normal pressure, the mixture is cooled under normal pressure or slightly pressurized, and the specific component X ₁ crystallizes under pressure. It is desirable to adjust the temperature to a temperature that is easy to change. For example, when the mixture at point A in FIG. 1B is cooled to a temperature T ₁ under normal pressure, crystallization of the specific component X ₁ is started, so that seed crystals are present, so to speak.
Therefore, when carrying out the second step of adiabatic pressurization, there is little concern that supersaturation will occur, and the amount of solid phase can be increased smoothly. Also, since the primary crystals are present, the amount of heat generated during solidification is small, and of course the heat of compression is also small, so the point at which the eutectic composition line X ₂ =Xe is reached is point F, which is on the lower temperature and lower pressure side than point G. Therefore, the amount of pressure increase is small, which is not only economical, but also allows the crystallization end point to be reached within a short time, which is more convenient for carrying out adiabatic pressurization. In the above description, it is assumed that both the container temperature and the temperature of the raw material mixture are room temperature (T ₀ ), and the temperature at the end point of crystallization is made to coincide with T ₀ . Therefore, the reproducibility of the crystallization cycle is improved, and the next compression separation step also has the advantage of being able to be operated at room temperature. If the physical properties and the like are known, the composition ratio and temperature after pressurization can be calculated from the amount of pressure increase, so the above advantages are highly feasible. Furthermore, in the above explanation, the mixture was pre-cooled to the temperature T ₁ (point B), but there is no problem in stopping the mixture at a temperature slightly higher than point B, and after further cooling to point B', adiabatic pressure is applied to H.
It is also possible to terminate the crystallization at a point. When cooled to point B', the raw material liquid either produces primary crystals or becomes supercooled, and in either case, it satisfies the characteristics of adiabatic pressure solidification. Although the difficulty of cooling under high pressure has been mentioned above, since the cooling in the first step is carried out under normal pressure or slightly increased pressure, the operation is extremely easy. This cooling may therefore be carried out in a high pressure vessel, but it is generally recommended that it be carried out in a separate step.

By the way, if a large amount of solid particles are dispersed in the mixed system before pressurization, the rate of increase in the solid phase due to pressurization is very fast. In ordinary substances, the solid phase increases at the same time as pressurization starts, and reaches almost the theoretical solid-liquid ratio in, for example, 1 to 5 minutes, but adiabatic pressurization is also useful in this case. In other words, high-pressure containers are generally thick-walled and have a large heat capacity, so if the container temperature is lower than the temperature of the mixing system, the mixture in contact with the container wall will rapidly solidify, causing scale-like crystals to form on the inner surface of the container. grow along. For example, if the temperature difference is 20° C., the crystal growth rate will be as high as 5 mm/min, causing the following harms.

Temperature distribution occurs inside the container, and the purity of the liquid phase within the container becomes non-uniform.

Impurities are entrained in the scale, which is difficult to separate.

The scale grows in a plate shape along the inner wall surface of the container, making it difficult to separate the liquid phase inside the scale.

However, such inconveniences can be avoided by forming a heat insulating layer, and can be similarly avoided in the case of substantially adiabatic pressurization due to rapid pressure increase.

Despite these explanations, as will be discussed later, in cases where the occurrence of scale is not a problem, i.e., when the purpose is not to produce ultra-high purity products, or when the purpose is to increase yield, etc. In some cases, it may be preferable to promote scale generation.

From the above explanation, it has become clear that crystallization promotion before adiabatic pressurization is effective. However, for slurry-like mixed systems that already contain a solid phase at room temperature and normal pressure, temperature control according to the first step of the present invention is effective. It is sufficient to assume that this has been achieved by a natural phenomenon and proceed directly to the second step, and it is natural that such a case is included in the present invention.

In addition, although the case of temperature adjustment (cooling) under normal pressure was mentioned above, the adjustment in the first step is
It may also be carried out under slight pressure. in this case,
The temperature of the mixing system rises briefly due to the heat of compression that comes with slight pressurization, and then it is cooled down to adjust the temperature, so the heat exchange efficiency within the mixing system is increased and a uniform state is achieved. This has the advantage that not only is the melting point of the low-melting point mixture raised, the generation of seed crystals becomes easier.

The first step (cooling) described above was a temperature control method for cases where the entire amount is in a liquid phase or mostly in a liquid phase, but in the case of a mixture that is in an entirely solid phase or a mostly solid phase at room temperature and normal pressure, , once all or a portion of the solid phase is dissolved to a state where the entire amount is in a liquid phase or most of it is in a liquid phase,
Compared to the above case, it is necessary to perform adiabatic pressurization on the high temperature and high pressure side. Of course, the significance of the presence of seed crystals is the same as the first cooling method, so
Overheating in the first step must be avoided. The mixed system, in which conditions similar to those during cooling have been created, is then adiabatically pressurized. The effect at this time is thought to be almost the same as the effect at cooling, but it goes without saying that the solid-liquid separation step also needs to be carried out in a high temperature range since high melting point compounds are being treated. do not have.

In the case of temperature control by pressurization, the unmelted raw material mixture is added to a liquid phase mixture in which the raw material mixture is completely melted to create a solid-liquid coexistence state, or the raw material mixture is mixed with a third substance such as a solvent. Of course, it is within the technical scope of the present invention even if the technology is replaced with a technology that utilizes a solid-liquid coexistence state by dissolving a large amount of solid, and the embodiments described in the claims are not limited to the present invention. It is not intended to limit the

When the first step is thus completed, the second step begins.Since the main points of adiabatic pressurization have been mentioned above, supplementary points of adiabatic pressurization will be described below.

Although high-speed pressurization was recommended as a means of adiabatic pressurization, for example, when pressurizing and solidifying the entire amount of benzene in an instant, the amount of heat generated is so large that it raises the temperature of benzene by as much as 100°C. Therefore, when using a thick-walled high-pressure vessel made of steel with large heat conduction and heat capacity, it is impossible to avoid a large amount of heat exchange even if the pressure is increased for a short time. Therefore, the formation of a heat insulating layer is even more desirable;
If a heat insulating layer is formed, the amount of heat transfer between the mixture and the container etc. will be significantly reduced throughout the entire process of injecting the stock solution at a temperature different from the container temperature, adiabatic pressurization, and compression separation, thereby further reducing the amount of heat transfer between the mixture and the container. It is a purpose. Also, if this insulation layer is made into two layers and a heater is placed in the middle,
By heating the heater in conjunction with the pressure increase rate or the rise in internal temperature, it is possible to bring the temperature of the heat insulating layer closer to the temperature of the mixture and further reduce the amount of heat transfer. As such a heat insulating layer, a synthetic resin such as phenolic resin is recommended as a material with a low heat capacity, but the material of the heat insulating layer is not intended to limit the present invention.

By the way, in the second step of the present invention, rapid pressure increase is recommended, but the crystals grown in this case tend to be finer as in the case of the rapid cooling crystallization method in which temperature is a parameter. In particular, increased viscosity due to high pressure intensifies this tendency. Moreover, since the liquid phase itself has a high viscosity, there is a problem that the next compression separation step is difficult. Therefore, by adding a third substance that mutually dissolves or easily mixes with the components of the mixed system, especially the mother liquor, the viscosity is lowered, crystal grains grow larger, and the solid-liquid separation becomes easier. method is used. This third substance is the same as the third substance such as the solvent mentioned above, and generally low viscosity solvents such as organic and inorganic solvents such as benzene, xylene, toluene, dioxane, and carbon tetrachloride are preferred, but in particular, It is preferable to use one that can be easily separated from the mother liquor and specific components by, for example, distillation.
Therefore, the third substance is not limited to a liquid, but may be a gas (including an inert gas) that does not react with the mixture components. Such a third substance is added within a range of 3 to 30% by weight based on the total amount of the mixture, but
The optimum amount can be selected depending on the composition, viscosity, and other conditions of the mixture.

In the second step carried out as described above, the solidification amount can be adjusted simply by controlling the pressure, but the amount of temperature increase at this time depends on the solid-liquid compressibility, thermal expansion coefficient, and solid-liquid coexistence ratio before pressurization. It can be determined as a function of temperature, etc. By the way, when pressurizing liquid-phase high-purity benzene at 5.4℃, the pressure required to solidify 10% is 300 atmospheres or more, and the amount of temperature increase at this time is
Close to 10℃. Also to increase solids by 50%
A pressure of 1,500 atmospheres or more is required and the temperature rises to around 40℃. Therefore, in order to effectively enjoy the effect of adiabatic pressurization in the present invention, at least 5
~10% solidification, preferably 5℃, preferably 10℃ from before pressurization
It is desirable that the mixture is such that the temperature can be increased above or above.

Such adiabatic pressurization is performed in a high-pressure container with a piston, in a pressurizing device installed separately from the solid-liquid separation section, or in piping connecting the two, but the Even if some heat may be released into the container, pressurizing device, piping, etc., the adiabatic pressurization of the present invention is satisfied as long as the heat is not actively dissipated.

In this way, heat is not actively radiated during adiabatic pressurization, but the mixture in solid-liquid coexistence state is locally cooled between the end of adiabatic pressurization and the next solid-liquid separation step. Radiation of heat is permissible within the scope of the spirit of the present invention, and is included within the technical scope of the present invention as a method for improving the solidification yield and growing crystal grains.

That is, in this method, after the adiabatic pressurization process is completed, the containers are left as they are for a while or are actively cooled, allowing heat to radiate only in a partial area, and then pressing and separating is started. For example, in Figure 1B, the temperature
Assume that a slurry at the same temperature is placed in a high-pressure container at T ₀ and as a result of adiabatically pressurizing it, point I is reached. Since the temperature of the mixture is naturally higher than the temperature of the container wall, T ₀ , the mixture near the container wall is cooled and gradually reaches J
Head towards the point. Therefore, for example, in the case of a cylindrical high-pressure container, the solid phase ratio inside the container gradually changes like a tree ring, and as time passes, it affects the center.
As a result, in the vicinity of the vessel wall, the eutectic point J' may sometimes be reached and even the eutectic line X ₂ =Xe may be exceeded. Therefore, solid-liquid separation should be performed before such a situation occurs; at that point, the solid-liquid coexistence material in the center of the container is I.
It is in the vicinity of the point and does not have a significant adverse effect on the purpose of the present invention. Rather, there is an advantage that not only can the crystallization rate be increased by cooling, but also the instability of fine crystals and slight supersaturation caused by rapid pressure increase can be eliminated by holding for a certain amount of time.

Therefore, based on this knowledge, a method can be proposed as a modification of the method of the present invention, in which the vessel wall is kept at a low temperature and heat is gradually radiated even during the adiabatic pressurization stage. That is, in this method, in the second step of the present invention, after the start of pressurization and before entering the solid-liquid separation step, the pressure is rapidly increased while gradually dissipating heat locally to the vessel wall to bring the solid-liquid coexistence state. Then you can rephrase it. Although this method has some aspects that are inconsistent with adiabatic pressurization, heat radiation is performed locally to the last, and the formation of a heat insulating layer is still preferred. As a result, the curve shown by A''→G becomes a curve similar to A''→G', and it is possible to suppress the non-uniformity within the system due to the temperature distribution to a relatively low level. Although this method can be applied to any mixture, it is advantageous when a high-pressure vessel or the like is used at room temperature in the separation of high-melting-point substances.

(2) Compression separation process The crystallization separation method under high pressure utilizes the fluctuation of the solid-liquid transformation line due to pressure. In the squeeze separation method when
When the piston 2 is further lowered from the step 2 to increase the squeezing pressure, the pressure P ₁ in the system becomes even higher, making it difficult to separate the mother liquor. By the way, it is known that in general mixtures, specific components solidify as the pressure increases. Therefore, the filter cake 5' in the vicinity of the filter 3 becomes increasingly dense, and the outflow resistance of the mother liquor becomes extremely large. That is, even if an attempt is made to promote solid-liquid separation by increasing the squeezing pressure, this will only solidify specific components in the mother liquor within the system, and if a certain limit is exceeded, this will have an adverse effect on the outflow of the mother liquor. Therefore, the present invention aims to ensure a passage for the mother liquor while dissolving a portion of the solids clogging the filter surface.

FIG. 4A is a conceptual diagram showing a state in which the crystal grains 6, 6 are densely packed near the filter surface, and the mother liquor L can hardly flow out.
That is, there is a considerable amount of mother liquor L on the surface of the large crystal grains 6, and fine crystal grains 6' are present in the gaps between them. When the pressure in the system is lowered in such a state, part of the crystals melts, the concentration of the specific substance in the mother liquor L increases, and the gap is enlarged. Moreover, since the fine crystals 6' have a large surface area, they melt relatively easily. Therefore, as shown in FIG. 4B, a passage for the mother liquor is secured, and when squeezing pressure is applied, the mother liquor easily flows out and moves toward the filter. Each time a dense grain layer is formed in this way, in other words, when the pressure P ₁ becomes significantly higher than the pressure P ₂ or when the pressure P ₂ becomes significantly lower than the pressure P ₂ at the beginning of separation. In other words, each time the filtration resistance increases, if the pressure inside the system or the region with high resistance is reduced, a passage for the mother liquor L is secured each time, and satisfactory compression separation can be continuously carried out. becomes possible.

By the way, in such a process of compression separation, the crystals near the filter first become relatively highly pure.
Since a low-viscosity mother liquid passes through these gaps, a portion of the surface of the high-purity crystal grains is inevitably melted in order to maintain a solid-liquid equilibrium state. Since the surface temperature of the crystal decreases as a result of melting, the crystal tends to be protected from melting. Therefore, it does not significantly reduce the solid yield (separation rate) and does not have any serious adverse effects in an industrial sense.

Next, specific methods of these operations will be explained based on FIG. 5.

FIG. 5A shows a phenomenon observed in the ordinary filter press method. That is, when a pressure difference begins to occur before and after the filter at point W (P ₁ > P ₂ ), the squeezing pressure is increased to P ₃ and the internal hydraulic pressure P ₁ increases rapidly, but the pressure P ₂ at the back of the filter is Since it remains at normal pressure, it does not change. As the liquid flows out due to squeezing and the filter becomes clogged, the pressure _P1 in the system gradually approaches _P3 , but in this state,
There are almost no liquid passages, and only partial compression separation takes place in the vicinity of the filter.

FIG. 5B is an example of the method of operation of the present invention. pressure
Suppose that solid-liquid compression separation is started at P ₃ and a difference begins to occur between the internal pressure P ₁ and the discharged liquid pressure P ₂ at point W. Needless to say, at the same time, the amount of mother liquor flowing out begins to decrease. At this time, if the pressure inside the high-pressure container is lowered, the mother liquor will flow out due to the above circumstances, so even if the same squeezing pressure _P3 is applied, _P1 and
P ₂ approaches and squeeze separation can still be carried out effectively. At this time, a compression pressure of P ₃ -P ₂ to P ₃ -P ₁ acts on almost the entire solid phase.

FIG. 5C shows another embodiment of the invention. When performing the above operation in a high-pressure container, a loss of squeezing force may occur when the solid phase of the mixture increases. This is due to the frictional force between the solid phase and the container wall, but P ₃ may be increased to compensate for this pressure loss. However, if it is increased too much, P ₁ may increase as shown by the chain line, leading to a situation where compression separation is impossible, so it should be kept within a range that compensates for the above loss.

FIG. 5D is an example in which the discharge liquid pressure is lowered in stages after FIG. 5B, and the pressure _P3 does not need to be kept constant and may be lowered as shown in _P'3 . FIG. 5E shows an example in which the discharge fluid pressure is continuously lowered from the beginning or from an arbitrary point, for example, point W.
P ₃ may be held constant as in the former case, or may be decreased in conjunction as in the latter case. FIG. 5F shows an example of separation in which separation is started at point Y, where solidification is progressing under pressure, and pressure is further increased to point W, where differential pressure begins to occur. Although P ₂ does not necessarily have to be lower than the pressure at point Y, it is preferable that it does not exceed the pressure at point W at least.

As explained above, at the point when a difference starts to appear between P ₁ and P ₂ , or when P ₂ starts to decrease from the point at which separation begins, the discharge liquid pressure, the pressure near the front of the filter, and then the pressure deep inside the high-pressure vessel The key point of the present invention is that the process is performed in such a way that the hydraulic pressure _P1 is also reduced. Therefore, the embodiments described in the examples and claims are not intended to limit the invention. For example, in a case where a considerable amount of mother liquor remains in the high-pressure container but the amount of mother liquor flowing out is essentially zero, the part away from the filter as shown by the chain line in Figure 5C. Since the liquid phase pressure P ₁ is clearly higher than the pressure P ₁ at the start of separation, it is possible to carry out the present invention without measuring P ₁ .

Also, in the above explanation, it was stated that P ₂ is lower than the pressure at the start of separation, or that P ₁ does not exceed the pressure at the start of separation, but during the progress of separation, both P ₁ and P ₂ are always lower. Adjusting is particularly effective. Figure 5D,
E was one example, but the separation operation was stopped at any stage of the separation process, the pressure and temperature were adjusted to melt a part of the solid phase, or the pressure was increased again. When restarting the compression separation after crystallization has proceeded by lowering the temperature or lowering the temperature, it is natural that the separation may be restarted at a pressure higher than the final pressure of the separation in the previous stage. It goes without saying that such a case is also included within the technical scope of the present invention.

Note that the pressure referred to herein does not mean only static pressure, but should also be understood as the effective pressure for discharging liquid even in the case of fluctuating pressure or pressure vibration based on hydraulic control. Further, the compression pressure applied to the solid crystal grain group acts in the direction of making the entire crystal grain group dense, and is usually several tens to hundreds of atmospheres, and sometimes reaches 1000 atmospheres. These pressure values are appropriately selected depending on the amount of crystals and crystal grain size of the mixture to be handled, the viscosity of the mother liquor, the target solidification and liquefaction, the distance from the filter, etc. Since this squeezing pressure acts on the contact surfaces between solid particles, the mother liquor is pushed out in the direction of the passage, and even when the pressure of the mother liquor is lower, this contact surface is maintained at a high pressure. Because of this, no significant melting occurs during the hydraulic stage.
Furthermore, although the above embodiment deals with a piston-cylinder type in which the filter is placed at the bottom of the cylinder, the present invention can easily be applied not only to cases where the filter is placed on the piston head or inside of the cylinder, but also to other compression mechanisms. Is possible.

(3) Solid extraction process Figure 6 shows an example of the equipment used to carry out this process.A heat insulating layer 11 is formed on the inner surface of the high-pressure vessel 9 as required, and hydraulically driven pistons 7 are installed on the top and bottom. , 8 are arranged. 12, 13, and 14 are pipes for liquid phase extraction, and are equipped with check valves 12a and 14, respectively.
13a and 14a are provided. Note that the piston 8 may be a lower plug fixed to the high pressure container 9. Also, 10 is a compressed solid, and 3 is a filter that is attached to the tips of the pistons 7 and 8 with a gap left, and of course moves together with the pistons.
One of the filters can also be omitted.

In this step, first, the pressure in the high-pressure container is returned to atmospheric pressure or a pressure in the vicinity thereof. As a result, some of the crystals of the specific component are melted, so liquid impurities that have adhered to the solid surface or remained in the gaps between the crystals are washed away and removed by the melting.
The remaining solid is covered with its own melt, resulting in a highly pure solid that is protected from contamination.

Various embodiments of this process can be considered, and the one described in the claims is just one example, but a typical method is to gradually reduce the pressure continuously or stepwise, and to remove the resulting melt. This is a method of sequential separation. Therefore, the pressure is not reduced to atmospheric pressure or a pressure close to it instantaneously, and the molten liquid is removed from the solid-liquid coexistence system each time, so that the temperature-lowering effect due to the heat of expansion of the molten liquid is small. Moreover, since this melted liquid is removed each time along with the impure liquid, the effect of removing the impure liquid is extremely high, and there is little drop in melting point due to impurities in the specific component crystals. Because of this, it is recommended that compression be performed at least once at any stage of successive pressure reduction to ensure sufficient solid-liquid separation. When the liquid phase is sufficiently removed by this squeezing, the polycrystalline particles of the specific substance are squeezed out, as in the case of powder compaction of metals, ceramics, etc. (mechanical press, rubber press, etc.), and huge block-shaped solid crystals are obtained. It will be done.

In general, in such compression, the higher the pressure is used, the higher the recovery efficiency of the solid phase is, and the lower the pressure is used, the higher the purity of the solid phase, and the stronger the solid phase block when it is exposed to atmospheric pressure. Therefore, it is desirable to perform many compressions in the process of stepwise or continuous pressure reduction, and more desirable effects can be obtained if compression is performed each time stepwise or in conjunction with continuous pressure reduction.

The degree of compression referred to here should be expressed as the difference between the average pressure in the solid-liquid coexistence phase and the pressure in the discharged liquid phase, and in most cases the pressure is tens to hundreds of atmospheres, and sometimes more than 1000 atmospheres. Therefore, good results can be obtained.

The block-shaped solid obtained as described above is finally depressurized to atmospheric pressure or a pressure close to it, and
After that, the high-pressure container is opened and taken out, but if the solid-liquid is separated by squeezing again just before taking out, or if the natural molten liquid or a part of the molten liquid is squeezed and separated after being taken out, the yield will be even higher. A solid of purity can be obtained. In particular, during compression after depressurization to atmospheric pressure, the pressure of the mother liquor in the stagnation area compressed at the back of the insulator, the gap between the piston and the container, etc. is released, so the liquid phase remaining in this stagnation area is separated and removed. It is effective in doing so. However, this squeezing is not necessarily an essential step, since this impure liquid phase can also be forced out as a gas before the solid is removed from the high-pressure vessel. Separation by such a gaseous body is
When the solid is already in the form of a block due to compression, it is effective in separating the mother liquor remaining in the stagnation portion and removing the molten mother liquor on the surface of the block. Furthermore, by squeezing the block solid phase at this time, the amount of melting caused by reduced pressure can be minimized.
It is preferable that the gas is one that does not react with the components of the mixture. Usually, a gas of several atmospheres, sometimes more than 10 atmospheres, is flowed from above or replaced with the remaining mother liquor. There is nothing special about replacing the remaining mother liquor in a vacuum.

Further, the above solid-liquid separation or solid removal operation by reducing pressure or squeezing can be made more effective by performing the treatment in a state where heat exchange between the high-pressure container and the internal object to be treated is cut off. In other words, when the temperature of the internal processed material decreases due to depressurization, a temperature difference occurs between it and the high-pressure container, but as a result, when heat flows in from the high-pressure container side, the high-purity solid phase becomes more concentrated than necessary. It will melt, and the temperature of the high-pressure vessel itself may drop, adversely affecting the next cycle. On the other hand, if a heat insulating layer is formed, the melting of the solid phase will be blocked from the influence of external conditions, making it possible to virtually control the operation only by pressure management, and ensuring uniformity within the high-pressure vessel. The advantages of pressure manipulation such as uniformity and uniformity of condition propagation can be meaningfully enjoyed. As such a heat insulating layer, a synthetic resin such as phenolic resin is recommended as a material with a low heat capacity, but the presence or absence of the heat insulating layer and the material thereof are not intended to limit the present invention.

If you try to heat and melt the entire remaining solid phase, for example, if the solid phase is 50 kg of benzene, the latent heat is 30 cal/g, so the total amount of
1500Kcal/50Kg is required, and even if heated with a 2KW heater, it would theoretically have to be heated for 75 minutes, and if heat conduction due to the heat outflow temperature gradient is taken into account, a longer heating time will be required. On the other hand, if the solid is to be discharged as it is, only about one minute is sufficient, and the impact on productivity is significant.

Furthermore, the surface of the solid taken out in the form of a block is
If the liquid contains a large amount of impurities and is wet, it can be easily separated dropwise by simply melting the block-shaped solid surface with hot air or the like. For convenience, the above explanation has mainly focused on examples of two-component simple eutectic mixtures, but this method may also be applied to multi-component eutectic mixtures or solid solution mixtures. Further, the specific component is not limited to one specific substance, but may be a eutectic or an intermolecular compound of two substances. In short, it can be applied to all mixtures in which components other than specific components are concentrated or diluted in the liquid phase as they solidify or melt under high pressure.

The present invention is constructed as described above, and its effects can be summarized as follows.

(1) The greatest advantage of pressure fractional crystallization (uniformity within the system) can be ensured under the best possible conditions.

(2) Since adiabatic pressurization can proceed within a short time, it is possible to shorten the cycle time of large industrial equipment.

(3) Impurities in the compression chamber can be discharged evenly and sufficiently.

(4) Specific components can be extracted in highly pure solid form.

Next, examples of the present invention will be shown.

Example 1 When a room-temperature mixture of m-cresol and p-cresol (mixing ratio 20:80) was rapidly pressurized in a high-pressure container with a heat insulating layer, a solid-liquid coexistence state was obtained at 40°C and 2000 atm. This was compressed to separate solid and liquid, and the compression was repeated while gradually reducing the pressure. When the remaining solid was returned to atmospheric pressure, it became a solid-liquid coexistence at 30°C. When this is immediately compressed and separated and the remaining solid (p-cresol) is taken out of the high-pressure container, it is 80% of the theoretical yield by compression at 2000 atm and 40°C, and the purity achieved is
It was 99.5%.

[Brief explanation of drawings]

Figure 1A is a graph showing the transition of the solid-liquid transformation point depending on temperature, Figure 1B is a graph showing the change and transition of the solid-liquid transformation point depending on pressure and temperature, and Figure 2 is a schematic cross section showing the progress of the squeezing process. Figure 3 is a graph showing the temperature change during reduced pressure, Figure 4 is an explanatory diagram showing the melting of crystals due to reduced pressure, and in Figure 5, A is a known filter press, and B to F are the respective operations of the present invention. A graph showing the process, and FIG. 6 is a sectional view showing an outline of the apparatus during solid removal. 1... High pressure vessel, 2, 7, 8... Piston, 3
...Filter, 5...Filter cake.

Claims (1)

[Scope of Claims] 1. A method for crystallizing one or more specific components from a mixture of two or more components and extracting the crystallized solid, the temperature of the mixture being lowered to atmospheric pressure. After adjusting the temperature under low or low pressure to a temperature at which the specific component is likely to crystallize by pressurization, the mixture is substantially adiabatically pressurized to solidify a part of the specific component or to form a solid phase. When the solid-liquid is compressed under high pressure and the liquid is separated through a filter, the pressure of the liquid phase to be separated after passing through the filter is equal to the point at which the filtration resistance begins to increase. The solid phase is squeezed while keeping the pressure lower than the pressure, and then the pressure on the solid phase is returned to atmospheric pressure or a pressure close to it to melt a part of the solid phase, and the remaining solid is removed from the high-pressure container. A material separation method that utilizes high pressure and is characterized by releasing and extracting the material. 2. The method according to claim 1, in which a heat insulating layer is formed on all or part of a high-pressure container, piping, pressurizing device, and accessory equipment to pressurize it. 3 Claim 1 in which the mixture is rapidly pressurized
Or the method described in Section 2. 4. The method according to claim 1, 2, or 3, wherein the mixture, which is entirely in liquid phase or mostly in liquid phase at room temperature and pressure, is cooled and then adiabatically pressurized. 5. The method according to claim 1, 2 or 3, wherein the mixture which is entirely solid or mostly solid at room temperature and pressure is heated and then adiabatically pressurized. 6 After the start of compression separation, when a difference begins to occur between the internal pressure on the solid phase side and the discharged liquid pressure, reduce the pressure in the solid phase storage section to lower the pressure of the separated liquid after passing through the filter. A method according to any one of claims 1 to 5. 7. Claims 1 to 7, which reduce the pressure in the solid phase storage section when the amount of liquid discharged from the filter starts to decrease after the start of compression separation to lower the pressure of the separated liquid after passing through the filter. The method described in any of Section 5. 8. The method according to claim 6 or 7, in which the discharge liquid pressure is continuously lowered stepwise. 9. Any one of claims 1 to 8, in which the solid in the solid phase storage section is squeezed so that the pressure of the unseparated mother liquor in the solid phase storage section does not become higher than the pressure at the time when the filtration resistance starts to increase. The method described in. 10 Claims 1 to 9, in which at least one compression is performed at any stage in separating the molten liquid when the pressure is returned to atmospheric pressure or its vicinity.
The method described in any of the paragraphs. 11. The method according to any one of claims 1 to 10, wherein the solid taken out of the high-pressure container is heated and partially melted and removed. 12 When separating the melt, at least 1
The solid phase from which the liquid phase has been separated by multiple compression is returned to atmospheric pressure or near atmospheric pressure, and the liquid phase is separated by flowing a gas while leaving it as it is or compressing the solid phase again. A method according to any one of claims 1 to 10. 13 Crystallizing one or more specific components from a mixture of two or more components,
A method for removing a crystallized solid, the temperature of the mixture being adjusted under atmospheric pressure or low pressure to a temperature at which the specific component is likely to crystallize due to pressurization, and then substantially adiabatic. After applying pressure to solidify a part of the specific component or increasing the solid phase to create a solid-liquid coexistence state, the mixture is locally cooled to advance solidification, and then the solid-liquid is heated under high pressure. When squeezing the solid phase and separating the liquid through a filter, the solid phase is squeezed while making sure that the pressure of the liquid phase to be separated after passing through the filter is lower than the pressure at the point when the filtration resistance begins to increase. Material separation using high pressure, which is characterized by returning the pressure on the solid phase to atmospheric pressure or a pressure close to it, melting a part of the solid phase, and releasing the remaining solid to the outside of the high-pressure container to take it out. Law.