JPH01270904A - Pressure crystallizing method - Google Patents

Abstract

PURPOSE:To recover crystal of a specified component with high purity at good yield by progressing crystallization of the specified component while measuring the temp. in a high-pressure vessel at a time of pressure crystallization and adjusting the pressure to the proper pressure between a pressure-temp. solid-liquid dissolution equilibrium line and a pressure-temp. supersaturation equilibrium line. CONSTITUTION:A mixed liquid raw material consisting of two or more components is held in a high-pressure vessel and the specified component is crystallized while keeping the pressure as a variable. In this case, both a pressure-temp. solid-liquid dissolution equilibrium line and pressuretemp. supersaturation equilibrium line of the above-mentioned specified components in the mixed liquid raw material are previously understood under such conditions that heat transfer of the inside of the high- pressure vessel and the outside of the system is practicably inhibited. At a time of executing pressure crystallization, crystallization of the specified component is progressed while measuring the temp. in the high-pressure vessel and adjusting the pressure to the proper pressure between the above-mentioned two equilibrium lines. As a result, crystal is made to a large size and crystal of the specified component can be recovered with high purity at good yield.

Description

Detailed Description of the Invention [Industrial Application Field] The present invention relates to a pressure crystallization method for fractional purification of a specific component from a mixture of two or more components containing the specific component using pressure as a control element. The present invention relates to an improved process that significantly increases purity and yield.

[Prior Art] Pressure crystallization is a method of purification by selectively crystallizing only specific components from a mixture of two or more crystalline specific components using pressure as a control element. It is attracting attention as a new purification method.

In other words, when a liquid (including solution and suspension, the same applies hereinafter) mixture containing specific components is pressurized to a high pressure of 1,000 atmospheres or more, only the specific components will selectively crystallize depending on the pressure. By squeezing and removing the mother liquor in this state, the target component can be recovered as a high-purity crystal of the specific component, or as a high-purity mother liquor if the mother liquor side is the target of recovery, especially when the volume at the time of liquid phase → solid phase transformation is It can be said that this is an extremely effective purification method for substances that undergo large changes.

[Problems to be Solved by the Invention] By the way, the yield of a specific component in pressure crystallization is determined by two main factors. The first factor is a theoretical factor based on the solid-liquid equilibrium state diagram of the specific component, and is determined by the concentration of the specific component in the stock solution and the operating conditions (pressure and temperature). The second factor is related to the shape and size of the precipitated crystals, and is determined by the crystallization conditions. The present invention provides an improved technique regarding the latter factor.

Conventionally, for example, when the crystal grains are made larger, the amount of mother liquor entrained between adjacent crystal grains is reduced, making it easier to filter and squeeze the mother liquor, which significantly contributes to improving the yield and purity of specific components. This has been expected.

However, in the pressure crystallization method that is currently in practical use, operating conditions such as pressure increase rate are almost uniformly determined depending on the performance of the pressurizing device, and the degree of supersaturation under the crystallization operating conditions is taken into account, and Strict management such as controlling the operating pressure while taking into account temperature changes accompanying crystallization of specific components is not performed.

The present invention has been made in view of these circumstances, and its purpose is to increase the size of crystals and increase the concentration of specific components by strictly controlling the crystallization operating conditions while taking into consideration the supersaturation state of the mother liquor. The aim is to establish a pressure crystallization method that allows crystals to be recovered with higher purity and better yield.

[Means for Solving the Problems] The configuration of the pressure crystallization method according to the present invention that can solve the above problems is that a liquid mixed raw material consisting of two or more components is stored in a high-pressure container, and the pressure is set as a variable. When carrying out the pressure crystallization method for crystallizing a specific component, the pressure-temperature of the specific component in the liquid mixed raw material is controlled under the condition that heat transfer between the inside of the high-pressure container and the outside of the system is suppressed as much as possible. The solid-liquid dissolution equilibrium line and the pressure-temperature supersaturation equilibrium line should be known in advance, and when performing pressure crystallization, the pressure should be adjusted to an appropriate level between the two equilibrium lines by measuring the temperature inside the high-pressure vessel. The gist of this method is to proceed with the crystallization of a specific component while adjusting the pressure to a certain level.

[Operations and Examples] As mentioned above, there is a close relationship between the particle size of the precipitated crystals, the precipitation rate, and the crystallization conditions. Crystallization operation
It is best to carry out the process under conditions such that new secondary crystal nuclei are not generated, specifically, under conditions where the concentration of the specific component to be crystallized does not reach supersaturation.On the other hand, in order to improve crystallization efficiency, the precipitation rate is Therefore, it is desirable to set the crystallization conditions close to the above-mentioned supersaturation concentration. However, as mentioned above, in conventional pressure crystallization, operating conditions cannot be said to be sufficiently controlled from this perspective.

Therefore, the present inventors conducted various studies in order to establish a crystallization operation management method that would increase the crystal size of a specific component and increase its yield and purity, and as a result, they came up with the following idea. I came up with the idea. In other words, the solubility and supersaturation concentration of a specific component in a raw material liquid are uniformly determined values corresponding to temperature and pressure, so they can be determined through basic preliminary experiments, and the solubility and supersaturation concentration of a specific component during pressure crystallization can be determined by basic preliminary experiments. The amount of temperature change associated with crystallization is also a value determined by physical constants such as the latent heat of fusion of the specific component, and the condition is to suppress heat transfer between the inside of the high-pressure container and the outside of the system as much as possible. In other words, assuming that pressure crystallization is performed under adiabatic conditions, if the specific heat and amount of the raw material liquid and the amount of actual temperature change during pressure crystallization are known, the amount of crystallization of the characteristic components at that time can be determined by calculation. I can do it.

Therefore, in the present invention, the condition is to perform adiabatic operation, and first, from the component composition and concentration composition of the raw material, as well as the initial temperature and pressure, for example, as shown in FIG. A dissolution equilibrium line and a pressure-temperature supersaturation equilibrium line are determined in advance, and operating conditions are set so as to fall within the shaded area between these two equilibrium lines.

In other words, the shaded area in Figure 1 represents the pressure-temperature conditions in which the growth of primary crystal nuclei of a specific component present in the raw material liquid progresses, but the generation of new secondary crystals does not occur. If, for example, operating conditions as shown by the solid line arrows are set within this region, the number of crystals can be reduced and the size thereof can be increased. During actual operation, the amount of temperature change in the crystallization treatment system is measured using a thermometer installed facing into the pressure vessel, and the amount of crystallization of specific component crystals and the accompanying concentration change of the specific component in the mother liquor are measured. Feedback control of the pressure is performed while continuously calculating by a computer or the like so that the operating pressure after the temperature change matches a preset operating line of the pressure-temperature correlation diagram. As a result, the number of specific component crystals obtained is suppressed to a small number according to the number of primary crystal nuclei (including those added as f!1 crystals) at the initial stage of crystallization, and only those existing crystal nuclei are grows and becomes something big. In conventional methods, such pressure control is not carried out appropriately, so new fine crystal nuclei are generated during the crystallization process, clogging the filter medium and impeding filtration.
There was a problem that not only did the pressing take a long time, but also a large amount of mother liquor components were trapped in the pressed cake, reducing the purity of the product.However, the present invention solves these problems at once, improving filtration and pressing efficiency. Product purity can be improved at the same time.

The present invention is roughly constructed as described above, but its feature is that the pressure-temperature solid-liquid equilibrium line and the pressure-temperature supersaturation equilibrium line are determined in advance according to the component composition and concentration composition of the raw materials, and the The trick is to measure the temperature during the crystallization process and perform feedback control so that the operating conditions are at an appropriate pressure between the two equilibrium lines mentioned above, and it is important to make effective use of these features. There are no restrictions on the specific configuration of the crystallizer, including the temperature/pressure measurement mechanism, pressure adjustment mechanism, filtration/squeezing mechanism, etc., as long as it is possible to do so. The basic operating conditions, including the steps involved, may be appropriately determined each time depending on the type and concentration of the specific component to be crystallized and the mother liquor component.

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

■The generation of fine secondary crystal nuclei during pressure crystallization is prevented, and primary crystal nuclei consisting of specific components can be obtained in a state of large growth, so there is no clogging in the filtration process, and the mother liquor is not clogged. can be efficiently compressed and removed, and both the yield and purity of specific component crystals can be increased.

■Since the time required for filtration and squeezing is shortened, the overall production time is shortened and productivity is improved.

■Since the screen does not get clogged, maintenance and management of the equipment is easy.

■Even if the target component is difficult to recover by filtration due to insufficient growth of crystal nuclei using conventional pressure control methods,
The present invention has made it possible to achieve sufficient crystal growth, and the fields to which pressure crystallization can be applied have been further expanded.

[Brief explanation of the drawing]

FIG. 1 is a diagram illustrating a pressure-temperature operation diagram used when carrying out the pressure crystallization method of the present invention. Figure 1 Pressure

Claims (1)

[Claims] When implementing the pressure crystallization method in which a liquid mixed raw material consisting of two or more components is placed in a high-pressure container and a specific component is crystallized using pressure as a variable, heat transfer between the inside of the high-pressure container and the outside of the system is possible. Under the condition of suppressing the A pressure crystallization method characterized by proceeding with the crystallization of a specific component while adjusting the pressure to an appropriate pressure between the two equilibrium lines by measuring the temperature within.