JPH0620488B2 - Specific component separation device - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION [Industrial field of application] The present invention is an apparatus for separating and purifying a specific component by utilizing a supercritical state, for example, silica, ferrite, rare earth oxide, apatite, titanic acid. The areas for refining salts and the like and collecting radioactive substances from radioactive wastes are related to a specific component separation device used for thinning or powdering, if necessary.

[Prior Art] As a technology for purifying a substance by utilizing a supercritical state, for example, hydrothermal synthesis of quartz is known. That is, the hydrothermal synthesis of quartz means silica (SiO 2) for water in the supercritical state.
The solubility of ₂ ) utilizes a phenomenon in which the solubility remarkably increases with an increase in temperature and pressure, and its principle is explained by FIG. 2 (a graph showing a solubility curve in the SiO ₂ —H ₂ O system). It That is, FIG. 2 is a graph showing the solubility of silica in water, and the critical point of water (374.9
It has been shown that the solubility significantly changes with changes in temperature and pressure in a region exceeding ℃, 218.5 atm), particularly when the pressure is 1000 atm or more. By the way, such a solubility greatly changes depending on the type of solvent and its acidity in the case of water, but for the same solvent, the solubility varies depending on the type of the solute to be extracted. It is natural. Due to this difference in solubility, a solute having a composition ratio different from that of the raw material is dissolved in the fluid in the supercritical state (for example, point A). When this supercritical fluid is brought to the state of point B or point C, the solubility decreases and solids precipitate. A,
Since the composition ratios of solutes at points B and C are naturally different, A →
The composition ratios of solids deposited in the processes of B, A → C and B → C are also different. For example, a deposit containing a specific substance between A → B and another specific substance at a higher ratio in B → C. The conditions can be set so as to precipitate. FIG. 3 is a schematic diagram showing a specific example of an apparatus for carrying out hydrothermal synthesis of crystal according to the above principle. The inside of the high-pressure container is divided into an upper chamber and a lower chamber via a perforated baffle, and water is supplied to the high-pressure container. It is sealed inside, and a waste crystal of quartz (base material) as a base material is arranged on the lower side, and a seed crystal is arranged on the upper side. Then, after enclosing the container, it is heated to a supercritical state, and the base material placement part (lower side)
If the seed crystal arrangement part (upper side) is heated to a higher temperature above the critical temperature and the seed crystal arrangement part (upper side) is kept at a lower temperature, the fluid in which a large amount of silica is dissolved in the base material arrangement part rises by convection and passes through the baffle. Into the seed crystal placement section, where it is gradually cooled. Silica supersaturated by cooling is deposited on the seed crystal, and a crystal (single crystal) grows there.

By using such a hydrothermal synthesizer, a silica single crystal can be grown from a base material containing a large amount of impurities. In the above device, the upper and lower parts of the same container are used, and the extraction is performed at the lower part and the precipitation is made at the upper part by utilizing the temperature difference, so that silica is substantially purified, but the time efficiency is low, and sometimes several times. It has to be done very gradually over the course of a week.
Therefore, it has been used only for synthesizing materials with high industrial added value such as crystal oscillators. In addition, the relationship between temperature and pressure changes greatly depending on the initial injection ratio of water to the volume of the container, and thus the solubility becomes unstable and stable synthesis is difficult. Incidentally, such single crystal growth using a supercritical state of water is called hydrothermal synthesis and is widely used in a specific field.

On the other hand, a supercritical gas extraction process can be mentioned as a refining technique utilizing the supercritical state. That is, the supercritical gas extraction process is mainly performed on an organic substance mixture system and is carried out by utilizing carbon dioxide or the like having a relatively low critical point, and basically comprises an extraction stage and a separation stage. That is, as can be understood from FIG. 4 showing the basic flow, the supercritical gas solvent and the raw material mixture are put into the extraction section, a specific component is extracted from the raw material mixture by the solvent, and then the extraction solvent is sent to the separation section. Then, the specific component is separated from the extraction solvent by expanding under reduced pressure here, and the gasification solvent separated from the specific component is released to the outside of the system as it is or compressed and then circulated to the extraction section.

By the way, in the supercritical gas extraction process, carbon dioxide or the like, which can be operated at a relatively low pressure because of its low critical point and has a large extraction capacity, is used as a solvent. However, although carbon dioxide (especially carbon dioxide in the supercritical state) is effective for extracting organic substances, it does not have sufficient extraction ability for inorganic substances, and because it includes a gas body compression step, It cannot be said that it is advantageous in terms of property and device economy.

[Problems to be Solved by the Invention] As described above, the hydrothermal synthesis process has applicability to inorganic substances such as silica, but there have been no examples of its use for separation and purification so far industrially. The supercritical gas extraction process has excellent separation efficiency, but lacks adaptability to inorganic substances such as silica, and there is a problem that this device is difficult to apply to the treatment of inorganic substances in the supercritical state of water.

The present invention has been made by paying attention to such circumstances, and it is possible to efficiently separate and purify mainly an inorganic substance by utilizing the supercritical state of a medium which is usually a liquid, and also consumes energy required for the separation. It is an object of the present invention to provide a specific component separation device that requires a small amount and can perform supercritical separation efficiently and promptly.

[Means for Solving the Problems] However, the present invention provides a pressurizing supply unit capable of pressurizing and supplying a liquid solvent to a pressure higher than a critical pressure; High temperature and high pressure part capable of maintaining above the critical temperature and critical pressure; a pressure adjusting mechanism that operates the pressurized supply part so as to prevent a pressure drop when a supercritical fluid flows out from the high temperature and high pressure part; and the high temperature The gist of the present invention is that the recovery part is connected to the outlet of the high pressure part and is controlled at a temperature and / or pressure lower than that of the high temperature high pressure part.

[Operation] The operation of the device of the present invention will be described below by taking the case of applying it to the purification and separation of an inorganic substance such as silica, but this does not limit the application target of the present invention.

As an extraction solvent for an inorganic substance such as silica, water or a liquid solvent such as an alkaline aqueous solution (hereinafter referred to as an aqueous solvent) may be adopted, and the pH can be arbitrarily adjusted depending on the target substance. As described above, the aqueous solvent placed in the supercritical state exhibits excellent extractability with respect to inorganic substances. Therefore, the aqueous solvent that has been heated and pressurized in the supercritical state is allowed to coexist with the raw material mixture containing the above-mentioned inorganic substance that is the target substance, and the target substance in the raw material mixture is sufficiently dissolved and extracted, and this extraction solvent is sent to the separation section. Solvent (gas or liquid) when fed and reduced pressure and / or cooled
Since the inorganic substance, which is a solute, solidifies and precipitates, the target substance can be separated. By the way, when using carbon dioxide as an extraction solvent, the critical point of carbon dioxide (critical temperature: 33.1
℃, critical pressure: 73 atm) is relatively low, so much energy is not required to heat and pressurize the solvent to the supercritical state, especially to the extraction section because the critical temperature is near room temperature and the critical pressure is low. Even when a commercially available high-pressure gas cylinder (150 atm) was used for the solvent supply, a sufficient supercritical state was obtained, and it was relatively easy to achieve the intended purpose.
However, in supercritical extraction using an aqueous solvent as the extraction solvent, the critical point of water is so high as described above that the supercritical solvent is supplied to the extraction section and there is a certain ability to extract this solvent at a specified pressure. A compressor with is required. Here, if the solvent to be compressed is a gas body such as carbon dioxide, it is necessary to perform a large amount of compression work, and the energy consumption becomes considerably large. On the other hand, when the object to be compressed is a liquid, a large amount of compression work can be performed even with furious power. In this respect, since the water-based solvent used in the present invention is a liquid at normal temperature and pressure, it is sufficient to perform liquid compression with a compressor, and there is an advantage that energy consumption for compression is extremely small. Although the solvent separated from the target substance in the recovery unit may be discharged as it is, it may be pressurized again and circulated to the extraction unit because it contains a small amount of the unrecovered target substance. In this case, the recovered solvent becomes a liquid when returned to near normal temperature and normal pressure, so that it is sufficient to perform liquid compression with a compressor as in the case of the new solvent, and the advantage of reduction of compression energy can be obtained.

The device of the present invention is a specific component separation device configured to carry out supercritical extraction using an aqueous solvent as an extraction solvent as described above, and as shown in the above configuration, a pressurized supply unit, a high temperature and high pressure unit and a recovery unit. It consists of the department as the main element.

The pressurizing and supplying section is a pressure increasing section for pressurizing the water-based solvent which is a liquid before compression to a critical pressure or higher and supplying it to the high temperature and high pressure section. ) Means pressurization up to a predetermined pressure capable of maintaining a supercritical state. The pressurizing means is not particularly limited, but a pressure booster or a water pressure pump is preferable. The high temperature / high pressure part is a part that receives and holds the pressurized solvent from the pressure supply part, and the extraction solvent is kept in a supercritical state in the high pressure chamber of the high temperature / high pressure part. In order to reach the supercritical state of the solvent pressurized to a pressure higher than the critical pressure in the pressure supply unit, the solvent must be heated until the temperature exceeds the critical temperature. Alternatively, it may be carried out in the process from the pressure supply unit to the high-temperature and high-pressure container, or both may be used together. External heating and internal heating can be considered for heating in high-temperature and high-pressure vessels, but since proper temperature adjustment is required to maintain the prescribed supercritical state properly without wasting energy, the vessel wall is required. The internal heat type in which the solvent in the container is directly heated is preferable to the external heat type in which the heating means is heated via, and it is desirable to incorporate the heating means in the high pressure chamber of the high temperature and high pressure container. The high-temperature and high-pressure container is provided with an outlet for continuously discharging the high-pressure solvent received from the pressure supply unit while keeping it in a supercritical state. The apparatus of the present invention is for extracting a target substance from a raw material mixture in such a high temperature and high pressure vessel, and therefore, a high temperature and high pressure vessel is provided with a charging port for feeding the raw material mixture in a batch manner or a slurry-like raw material mixture. An injection line for continuously injecting into the high temperature and high pressure container is provided. The recovery unit provided next is a part that receives the supercritical solvent from which the target substance has been extracted in the high temperature and high pressure container and separates and recovers the target substance from the supercritical solvent. Since it is necessary to adjust to a low temperature and / or low pressure, the recovery section is provided with a mechanism for performing such temperature control or pressure control. However, the method of lowering only the temperature while maintaining the pressure equivalent to that of the high temperature and high pressure section requires the recovery section to have pressure resistance equivalent to that of the high temperature and high pressure section, and it is necessary to dissipate heat. The physical burden will increase. However, the heat can be dissipated substantially by using a pipe from the high temperature and high pressure section to the recovery section.

It is also possible to adopt a method in which the target substance is separated and recovered from the supercritical solvent by positively lowering the pressure to a predetermined pressure. As such a pressure control type recovery part, a recovery part in which a back pressure applying device is connected can be exemplified, and the back pressure applying device itself is a variable capacity type high pressure container, and this container is used as the recovery part. But it's okay. The recovery unit may be formed of a single container, but may be one in which two or more containers are arranged in parallel. In this case, when one is operating, the collected product can be switched from the other to be used. Although the above description has been made on the assumption that the target substance to be extracted is one, it is also possible to extract two or more target substances from the raw material mixture. In this case, the target substance is extracted from the high temperature and high pressure container. The supercritical solvent can be sequentially introduced into the recovery section where the separation temperature and pressure conditions are gradually reduced, and the target substances can be separated and recovered from each other due to the difference in the solubility of the target substances in the solvent. It is effective to form two or more recovery containers with different pressure / temperature conditions in series to form the recovery unit.

The back pressure applying device is not limited to the variable displacement type high pressure container, but may be an orifice, a throttle valve, or the like and can be controlled by the flow rate. For example, if orifices are provided at the inlet and the outlet of the recovery section, the recovery section can be maintained at a temperature and pressure lower than those of the high temperature and high pressure section and at a pressure higher than atmospheric pressure.

The residual solvent after separating and recovering the target substance in such a recovery unit may be discarded, or may be sent to the pressure supply unit again and pressurized to a pressure higher than the critical pressure and supplied to the high temperature and high pressure unit. In this case, as described above, the extraction solvent used in the present invention is an aqueous solvent, and the solvent to be supplied is in a liquid state. Therefore, if the temperature and pressure are appropriate below the supercritical point, it is repressurized as a liquid. It can be supplied to the liquid supply part.

[Examples] FIG. 1 is a schematic view showing a specific component separation apparatus according to the present invention, wherein 1 is a pressure booster, 2 is a high temperature and high pressure container, 3a and 3b are recovery containers, and 4 is a back pressure applying device.

The high temperature / high pressure container 2 is formed of a pressure resistant container 6 with a lid 5 capable of withstanding a high temperature / high pressure above the critical point of water. A filter F is disposed in the container and a heater B is built in the bottom of the container 2, Further, a heater A is also arranged on the outer circumference of the container 2. A high pressure solvent inlet 9 is provided at the bottom of the pressure vessel 6 and a lid 5 is provided.
A supercritical solvent discharge port 10 is formed in each. On the other hand, the collection containers 3a and 3b have solvent introduction ports 11 and 12, and
Solvent discharge ports 13 and 14 are provided at the bottom, and recovery containers 3a and 3
b is connected in series, and the recovery container 3b on the downstream side and the cylinder portion 7 of the back pressure applying device 4 are connected by a line l ₃ . And the cylinder part 8 of the pressure booster 1 and the high temperature and high pressure container 2
With high solvent inlet 9 is contacted by the line l ₁ of
Supercritical solvent discharge port 10 of high-temperature high-pressure container 2 and recovery container 3a
The solvent inlet port 11 of the contact in the line l _2, line l _1, l _2, respectively heaters C and the heater D in is provided along the line. Orifices R ₁ , R ₂ and R ₃ are provided in the discharge line, which becomes a resistance against the flow of the solvent and the pressure is gradually decreased.

In such a specific component separation device, the lid 5 is opened, the raw material mixture M is charged into the high temperature and high pressure container 2, and the container is hermetically sealed. Then, water pumped up from the storage tank T _{1 is} supplied to the line l ₁ It is introduced into the high-temperature high-pressure container 2 via.
While passing through the line l ₁ , the water is pressurized to a pressure exceeding the critical pressure by the pressure intensifier 1 and heated to a considerably high temperature by the heater C. The high-temperature high-pressure water introduced into the high-temperature high-pressure container 2 is the external heat heater A installed in the high-temperature high-pressure container 2.
And is further heated by the internal heater B to exceed the critical point of water and become a supercritical fluid. In the high-temperature high-pressure container 2, the raw material comes into contact with the supercritical fluid, and the extraction of the target component by the supercritical fluid proceeds. The supercritical fluid from which the target component has been extracted passes through the filter F, is discharged from the discharge port 10 and is introduced into the recovery container 3a through the line l ₂ . Here, the recovery containers 3a and 3b are the back pressure applying device 4 as described above.
The internal pressure is adjusted by advancing and retracting the piston of the back pressure applying device 4. The solvent may be finally collected in the container T ₂ by applying a back pressure with the orifice or the throttle valve R ₃ or the like. In addition, the collection containers 3a, 3
Externally heated heaters E ₁ and E ₂ are respectively provided in b to adjust the temperature. However, this heater can be omitted depending on the properties of the target substance and the pressure of the container of the recovery container, and in some cases, cooling is also required. High-temperature high-pressure water via line l ₂ is collection container 3a which is controlled to a predetermined temperature and pressure in this manner, sequentially introduced into 3b, the target substance each collection container 3a, separated and deposited within 3b. The temperature and the pressure at this time are T ₁ > T ₂ and / or P ₁ > P ₂ between the high temperature and high pressure container 2 and the recovery container 3a, and T ₂ > T ₃ between the recovery container 3a and the recovery container 3b. And / or P ₂ > P ₃ may be set, whereby the target substance is separated / precipitated from the aqueous solvent that has become a gas or a liquid.
And the collection container 3b is discharged is extremely small state of water or water vapor of the target substance content, is stored in the tank T ₂ via line l _3. The water or water vapor in the tank T ₂ can be cooled or pressurized to form water that does not contain steam, and then can be circulated to the pressure booster 1 for circulation.

In FIG. 1, the pressure adjusting device P. C. Is provided. This keeps the internal pressure of the high-pressure and high-temperature part at a predetermined value, and prevents the pressure from decreasing with the outflow of supercritical fluid,
Alternatively, it is used to prevent an excessive increase in pressure.When using a pressure booster as a pressure supply device, a hydraulic pressure regulator that supplies the pressure booster and a relief valve are used when using a pump. Alternatively, the pressure supply device may be electrically controlled.

Further, in the apparatus of the present invention, in order to achieve the pressure conditions of P ₁ > P ₂ and P ₂ > P ₃ , pressure reducers R ₁ , R ₂ are installed in the transfer line.
The pressure control is performed by a combination of the back pressure applying device and the pressure reducer, but it is also possible to control the pressure by either one.

Further, in the above apparatus, the internal heat type heater B is arranged in the high temperature and high pressure container 2. However, since the heater B is exposed to the high temperature and high pressure atmosphere, in order to avoid contact leakage with water, steam or the like in the container. Must have a sufficient sealing structure, and a sheath type heater can be exemplified. Further, if the contents are acidic or alkaline, the sheath tube itself may be dissolved or corroded, so it is necessary to use a sheath tube having appropriate corrosion resistance according to the contents. Furthermore, it is also possible to divide the internal heat type heater axially into upper, interrupt, and lower stages to arbitrarily determine the vertical temperature distribution.

In addition, when the high-temperature high-pressure fluid is caused to flow from the high-temperature high-pressure vessel 2 to the recovery vessels 3a, 3b, the fluid may be cooled in the transfer line and the target substance may be deposited in the line. In particular, if it is made to flow out at a high speed, internal energy is converted into kinetic energy and the temperature of the fluid is lowered, so that there is a great risk of precipitation. As a result, the transfer line and the pressure reducer may be blocked by the deposit. In order to prevent this, in the above apparatus, an external heater D is installed in the transfer line ₁₂ to cool the target substance.
It is heated so that precipitation does not occur. The heater is more preferably an internal heat type heater.

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

(1) An inorganic substance can be efficiently extracted and separated from a raw material mixture in a short time.

(2) Since the extraction solvent is recovered in liquid form and can be reused, the compression efficiency is high and the energy consumption can be reduced compared to the system that requires gas compression. That is, the operating cost can be reduced.

[Brief description of drawings]

FIG. 1 is a schematic diagram showing a specific component separation device of the present invention, FIG.
The figure is a graph showing the change in dissolution of SiO ₂ —H ₂ O system,
FIG. 4 is an explanatory diagram showing a hydrothermal synthesis apparatus for quartz, and FIG. 4 is an explanatory diagram showing a basic flow of a supercritical gas extraction process. 1 ... Intensifier, 2 ... High temperature / high pressure container 3a, 3b ... Recovery container, 4 ... Back pressure applying device AE ... Heater

Claims (6)

[Claims] 1. A pressurizing supply unit capable of pressurizing and supplying a liquid solvent at a pressure higher than a critical pressure; connecting the liquid solvent outlet of the pressurizing supply unit and maintaining the inside at a critical temperature and a critical pressure or higher. A high temperature / high pressure part capable of operating; a pressure adjusting mechanism for operating the pressure supply part so as to prevent a pressure drop when a supercritical fluid flows out from the high temperature / high pressure part; and the high temperature / high pressure part connected to the outlet of the high temperature / high pressure part. A specific component separation device comprising a recovery unit controlled to a temperature and / or pressure lower than that of the unit. 2. The specific component separation device according to claim 1, wherein the recovery part is pressurized by a back pressure applying device. 3. The specific component separation device according to claim 1 or 2, wherein two or more recovery units are provided in series or in parallel. 4. The specific component separation according to claim 2 or 3, wherein the back pressure applying device is a high-pressure container including a variable displacement type high pressure chamber, and the variable displacement type high pressure part is a recovery part. apparatus. 5. The specific component separation device according to claim 1, wherein the pressure drop in the high temperature and high pressure section is compensated by the operation of the pressure supply section. 6. The specific component separation device according to claim 1, wherein a heater for heating is built in a high pressure chamber of the high temperature and high pressure section.