JPH046401B2 - - Google Patents

Description

[Detailed description of the invention] [Industrial application field] The present invention is based on a mixture of specific components and impurities.
Regarding pressure crystallization methods that can recover specific components in high yield in a single operation, pressure crystallization is particularly suitable for recovering specific components from raw materials containing specific components that are solid at room temperature or from high-concentration raw materials. It is about the method.

[Prior art] Pressure crystallization is a method in which a liquid phase consisting of multiple components or a raw material (fluid phase mixture) consisting of a solid-liquid mixture is introduced into a high-pressure container, and the raw material is drained with the drain pipe closed. This is a method in which high pressure is applied to accelerate the crystallization of a specific component, and by this operation, a state in which crystals (solid phase) of the specific component and liquid phase other than the specific component are mixed is obtained. Therefore, by unblocking the drain pipe, applying pressure to the solid-liquid coexistence state, and draining the liquid phase component out of the system via a filter, and separating the solid and liquid while squeezing the remaining solid phase, high purity can be identified. ingredients can be obtained.

[Problems to be Solved by the Invention] The present inventors have been involved in the development and industrialization of pressure crystallization methods, and are also conducting various studies to improve the recovery rate of specific components.

Basically, however, the recovery rate can be increased by increasing the crystallization pressure. However, there is a limit to the operating pressure, and obtaining a pressure exceeding 3000 Kgf/cm ² is not advantageous in terms of equipment cost. Furthermore, if the pressure crystallization operation is repeated several times, the recovery rate of the raw material can naturally be increased, but the throughput per container volume must be sacrificed, which inevitably leads to a decrease in productivity.

In this way, it is difficult to improve the recovery rate while satisfying economic efficiency, especially when handling highly concentrated raw materials or in pressure crystallization of raw materials where the specific substance targeted for recovery is solid at room temperature. is even more difficult.

The inventors of the present invention were concerned about these circumstances and conducted further research with the aim of improving the recovery rate.

That is, FIG. 1 is a graph showing the solid-liquid equilibrium relationship of a pure substance, a mixed raw material with a certain composition ratio, and a mixed raw material with a eutectic composition ratio as a function of pressure and temperature.
a is the solid-liquid equilibrium line of a pure substance (100% specific component);
b shows the solid-liquid equilibrium line of a mixed raw material with a certain composition ratio (specific component: x%), c shows the solid-liquid equilibrium line of a mixed raw material with a eutectic composition, and each compositional component has a liquid phase at the lower right side of each line. The solid state is shown on the upper left side. Note that b ₁ point means the solid-liquid equilibrium point of the above raw material under atmospheric pressure, and T ₁ means the melting point of the specific component under atmospheric pressure. Here, when the above raw material containing x% of the specific component is charged into the pressure crystallizer and subjected to pressure crystallization, the raw material temperature at the time of charging into the pressure crystallizer (i.e., the raw material temperature under atmospheric pressure) is T. ₂ , T ₃ , T ₄ , T ₂ in the figure is b ₁
Since T 3 is on the right side of the point, the raw material at that temperature will be in a liquid state, and since T ₃ is slightly to the left of the point b ₁ , the raw material at this temperature will be in the form of a slurry with a small amount of solids mixed in, and furthermore, at the temperature T ₄ The raw material is in the form of a slurry containing a significant amount of solids. In this way, when raw materials with different temperatures and properties are sealed in the equipment and pressurized, the pressure and temperature of each raw material increases along the α, β, and γ lines, accompanied by heat generation due to pressurization. and reaches points A, B, and C. Note that the points A, B, and C are set so that the vertical axis (crystallization pressure) value is the same value (maximum pressure here) _P1 . Then, by separating the crystallized crystals (solid phase) from the liquid phase while maintaining the pressure and squeezing the solid phase remaining in the high-pressure container, a highly pure specific component can be obtained. The specific components at this time are A, B,
An amount corresponding to the difference in equilibrium concentration between each point C and the solid-liquid equilibrium point _b2 of the raw material at the crystallization pressure can be recovered. That is, to _the left of point b (solid phase side)
The recovery amount of specific components increases as the distance from C
At the same time, a large amount of a specific component can be obtained.
Therefore, it can be seen that in order to increase the recovery amount, that is, the recovery rate, it is effective to lower the temperature of the raw material when it is introduced into the pressure crystallizer as low as possible. However, if the point reached after pressurization exceeds the eutectic solid-liquid equilibrium line c, the eutectic will be mixed into the solid phase, making it impossible to obtain a pure specific component. Therefore, it is necessary to lower the raw material charging temperature within a range where the point reached after pressurization is as close as possible to the eutectic solid-liquid equilibrium line c, thereby increasing the recovery rate of the specific component.

However, if the charging temperature to the pressure crystallization vessel is changed from T ₃
When decreasing in the direction of T ₄ , the solid phase content in the raw material increases and the slurry concentration increases. Slurry concentration
It is generally difficult to transport raw materials with a content of 25 to 30% or more through pipes, and as described above, the method of lowering the raw material charging temperature in order to increase the recovery rate is to use the conventional method of transporting raw materials in pressure crystallizers (piping transport). I have no choice but to reach my limits. In addition, the solid phase content in slurry raw materials with a large solid phase content is originally a solid containing impurities,
Even if such a slurry raw material is subjected to a pressure crystallization operation, crystallization of the specific component proceeds using solids containing impurities as nuclei, so it is not possible to obtain a highly pure specific component solid.

The present invention was completed based on these research results and as a result of further research to provide a method that can economically improve the recovery rate of specific components.

[Means for Solving the Problems] That is, the method of the present invention is to collect a solid or slurry raw material consisting of a specific component and an impurity component with a solid content concentration of 25% or more from the upper opening of a high-pressure container having a large diameter. After charging into a high-pressure container and sealing the upper opening of the high-pressure container, a high-temperature liquid or slurry raw material with a solid content concentration of less than 25% consisting of specific components and impurity components is injected, followed by a pressure crystallization process. The gist lies in the transition to .

[Operations and Examples] As mentioned above, in order to increase the recovery rate, it is necessary to charge low-temperature raw materials into a high-pressure container, but when the raw material charging temperature is lowered, the raw material becomes slurry-like with a high solid content. Further, it loses its fluidity and finally becomes completely solid. Such raw materials cannot be transported even using slurry pumps.

In the method of the present invention, by lowering the charging temperature in this way, the slurry raw material or solid raw material (mixture of specific components and impurity components) whose solid content concentration has increased by 25% or more is first placed in a high-pressure container. Insert into. The method is to open the lid at the top of the container to a large diameter, and use an appropriate slurry supply system depending on the slurry concentration, such as a piston system or a bucket conveyor. By the way, in this state, the solid content in the charged raw material is aggregation of fine single crystals to form a lump, and liquid impurities or crystallized products of these exist in the gaps between adjacent single crystals. Further, when the slurry concentration is very high, gas such as air may be present in the gaps between the lumpy solids. Furthermore, although the single crystal itself has high purity in the center, the purity decreases as it approaches the outer surface, and the outermost surface may be covered with low-purity crystals. Therefore, if the pressure crystallization operation is continued as it is, these impurities will be trapped and crystallization will proceed without being removed, making it impossible to obtain a specific component of satisfactory purity. Furthermore, when the amount of solid phase is large, the gas and intervening space ratio is also high, and the efficiency of using the internal volume of the container is reduced. Therefore, after sealing the high-pressure container for the purpose of increasing the purity of solid content at the time of charging or increasing the usage efficiency of the container, a high-temperature liquid raw material consisting of specific components and impurity components or a high-temperature slurry with a solid content concentration of less than 25% is prepared. The raw material is injected into a high-pressure container. There is no particular restriction on the raw material to be injected at high temperature, but for example, by heating a raw material containing specific components and impurity components in the same proportions as the aforementioned raw materials or in different proportions, the temperature of the raw material injected from the top of the container may be lowered. It is possible to use a liquid obtained by dissolving some or all of the solid content at a high temperature, or a separated waste liquid obtained by a pressure crystallization operation in the pre-charging process. By injecting this liquid or slurry high-temperature raw material, the high-temperature liquid enters the surface of the solid content in the initially charged raw material or the voids between the solid content, dissolves low-purity crystals or impurity crystals, and turns into a liquid phase. Transition. The temperature of the charging material system also increases. Further, by applying pressure, the solid space completely disappears. Additional supply of liquid or slurry raw material is performed by a liquid pump or slurry pump, etc., and is supplied under pressure as necessary, so that the internal gas space is substantially eliminated. Incidentally, as a result of the above, the solid content remaining in the slurry-like raw material becomes highly pure, and this serves as a nucleus to proceed with favorable pressure crystallization as described below. That is, as in the conventional pressure crystallization method, as the pressure inside the high-pressure container is increased, the air bubbles mixed in when charging the raw materials are also dissolved in the liquid, and the liquid sufficiently penetrates between the solid contents. At the same time, specific components in the liquid phase crystallize around the remaining solid components as nuclei. Once the pressure has been increased to a predetermined level, operations such as separating and discharging the liquid phase, sweating, squeezing, and taking out the specific component crystal cake in the form of a cake are performed according to the standard separation method of conventional pressure crystallization methods. By these methods, a highly purified target substance can be obtained in good yield.

In order to further increase the purity, the above-mentioned high-temperature raw material may be injected two or more times. That is, when the first pressure crystallization operation is completed, the high temperature raw material is again injected without removing the target substance, and then the pressure crystallization step is started.
By repeating this process, the purity of the specific component can be increased. In this case, it is preferable not to perform compression for each cycle, but to perform compression only in the final cycle.

The basic structure of the method of the present invention is as shown above, but as is clear from the above explanation, when attempting to implement the method of the present invention, pipe transportation is required for charging low-temperature slurry or solid raw materials. Therefore, it is necessary to open the upper side of the high-pressure container and charge the raw material G into the high-pressure container 1 through, for example, a retractable supply port H (see FIG. 5). The pressure crystallizer used in the method of the present invention satisfies these demands, and includes a rigid high-pressure container, a piston configured to move back and forth within the container from one side of the container to the other, and the piston. The container is provided with an end cover that closes the open end of the rigid high-pressure container from the opposite side, and is constructed such that at least the upper side of the rigid high-pressure container can be opened and closed. For example, as shown in FIG. 2, if the piston 2 is moved forward and backward from the lower side of the rigid high-pressure container 1, an end cover 3 that can be opened and closed is provided on the upper side. When charging the slurry raw material or the solid raw material G, the piston 2 is moved backward, and the raw material G is inserted from the upper side. When charging the raw material G, when the slurry concentration is high, it is difficult to evaluate the charging amount because the number of voids increases. Therefore, an appropriate amount roughly corresponding to the capacity of the high-pressure container is measured in advance by weight or volume and injected. For injection, a method suitable for the slurry concentration of the system to be handled is selected, such as the screw feeder method (see Figures 7 and 8), bucket method, piston method, shooter method, etc.

After the raw materials have been charged in this manner, the end cap 3 is fitted as shown in FIG. 2, and the high temperature liquid or slurry raw material L is injected through the channel 4 formed in the end cap 3.
Thereafter, the piston 2 is advanced to pressurize the raw material, and operations subsequent to crystallization can be performed. When removing the target substance S, remove the end cap and remove the piston 2.
The target substance S may be pushed up by the advance of the target substance S.

Further, as shown in FIG. 3, in a structure in which the piston 2 is moved forward and backward from the upper side of the rigid high-pressure container, a removable end cover 3 is provided at the lower end. When charging the slurry raw material or the solid raw material G, the piston 2 is pulled out, and after charging the raw material G from the upper side, the piston 2 is inserted and the inside of the high pressure container is sealed. The high temperature raw material L in liquid or slurry form is injected through the flow path 4a formed in the lid 3, and a normal pressure crystallization operation is then performed. Incidentally, in order to take out the target substance S, the high pressure container 1 may be raised together with the piston 2.

Fig. 4 shows a modification of Fig. 3, in which a push-up mechanism K is attached to the end cover 3 placed on the lower end side of the high-pressure container, and when the crystallization is completed, the rod R of the push-up mechanism K is attached after the piston 2 is extracted. is advanced to push up the target substance S, thereby taking out the target substance S.

In these descriptions, a structure is mentioned in which the product is removed upwardly in the form of a cake. In a pressure crystallizer, separated mother liquor is collected behind a filter or the like (not shown) built into the container, and when the lower lid is opened to take out the mother liquor, this liquid drips out downward. Therefore, a device mechanism is required to collect these dripping liquids, but when the product cake is removed from the upper lid, there is no such problem, and the remaining mother liquor flows out together with the draining liquid in the next cycle.

In addition, as shown in FIG. 6, pressure crystallizers M and Ma consisting of two sets of high-pressure vessels 1, etc. are prepared for the pressurizing drive mechanism J that advances and retreats the piston 2, and one pressure crystallizer M performs crystallization. While the process is progressing, the charging of the slurry or solid raw material to the other pressure crystallizer Ma is completed, and when the crystallization is completed, the pressure drive mechanism J is moved laterally to prepare it. Perform pressure crystallization using a pressure crystallization device Ma. Thereby, the pressure crystallizer can be operated efficiently. Although two pistons 2 are used in the figure, it is also possible to use one piston.

[Effects of the Invention] The present invention is configured as described above, and can obtain the effects summarized below.

(1) In the method of the present invention, first of all, the solid content concentration is
A slurry-like raw material or a solid raw material with a concentration of 25% or more is charged into a high-pressure container from the upper open part of the high-pressure container, and after the high-pressure container is sealed, the raw material is heated as necessary to remove a portion of the solid content. Alternatively, the high-temperature raw material that has been completely dissolved is injected into the high-pressure container, so that the temperature at which the raw material is charged into the high-pressure container can be lowered, and crystals of the specific component can be obtained at a high yield. In addition, in the case of a raw material with a high solid content, the solid content contained in the raw material contains impurities in the surface layer or between solid contents, and there are many voids, but in the method of the present invention, the high pressure container is sealed as described above. Since a high-temperature raw material with a low solid content is then injected, the impurities are melted and transferred to the liquid phase, and specific components are then crystallized by pressure crystallization. Therefore, it is possible to obtain specific component crystals of satisfactory purity with improved yield.

[Brief explanation of drawings]

Figure 1 is a graph showing the solid-liquid equilibrium point in adiabatic pressure crystallization as a function of pressure and temperature.
FIG. 4 is a flow explanatory diagram showing the pressure crystallization method according to the present invention, and FIGS. 5 to 8 are schematic diagrams showing modifications of the apparatus used in the method of the present invention. 1... High pressure container, 2... Piston, 3... End cap, 4... Channel, G... Slurry raw material or solid raw material with a solid content of 25% or more, L... Liquid or slurry high temperature raw material .

Claims (1)

[Claims] 1 When performing a crystallization method that uses pressure as a variable, a solid or slurry raw material consisting of a specific component and impurity components with a solid content concentration of 25% or more is charged into a high-pressure container from the upper opening of the high-pressure container. After sealing the upper opening of the high-pressure container, the high-temperature liquid or solid content consisting of specific components and impurity components is 25%.
A method for pressure crystallization of a highly concentrated raw material, characterized by injecting a slurry-like raw material with a concentration of less than 100 ml through a pipe, and then proceeding to a pressurized crystallization step.