JPS63205102A - Specific component separation device - Google Patents

Abstract

PURPOSE:To separate and refine specific components, especially inorganic materials with reduced energy consumption for separation by utilizing the supercritical state of a medium which is normally in a liquid phase. CONSTITUTION:A raw material mixture M is charged into a high-temperature high-pressure vessel 2 by opening a lid 5, and the vessel 2 is sealed hermitically. Then water pumped up from a storage tank T1 as a solvent is pressurized to a pressure level beyond a critical pressure by a pressure increasing device 1 while it is passed through a line l1, and is introduced into the vessel 2. After this, the water is heated up by heaters A, B to a fluid in a super critical state, and the raw material M and the fluid in the supercritical state are allowed to contact each other in the vessel 2 to promote extraction of objective components with the help of the fluid in supercritical state. Next, the fluid in supercritical state after extraction of the objective component is discharged from a discharge outlet 10, and sequentially guided into recovery containers 3a, 3b controlled to a predetermined temperature and pressure via a line l2. Finally the objective components are separated and deposited in the recovery containers 3a, 3b respectively.

Description

DETAILED DESCRIPTION OF THE INVENTION [Industrial Field of Application] The present invention is an apparatus for separating and purifying specific components using a supercritical state, such as silica.

The present invention relates to a specific component separation device used for refining ferrite, rare earth oxides, apatite, titanate, etc., recovering radioactive substances from radioactive waste, or forming thin films or powders as necessary.

[Prior Art] Hydrothermal synthesis of quartz crystal, for example, is known as a technique for purifying substances using a supercritical state. In other words, hydrothermal synthesis of quartz refers to the synthesis of silica (Si02
) takes advantage of the phenomenon that the solubility of
Graph showing the solubility curve in the S i 02-H,O system). That is, FIG. 2 is a graph showing the solubility of silica in water, and the critical point of water (374,
9℃, 218.5 atmospheres), especially in areas where the pressure exceeds 100 degrees
It has been shown that in the case of 0 atm or higher, the solubility changes extremely with changes in temperature and pressure. By the way, such solubility varies greatly depending on the type of solvent and, in the case of water, its acidity, but the solubility in the same solvent varies depending on the type of solute to be extracted. Of course. Due to this difference in solubility, a solute having a composition ratio different from that of the raw material dissolves in the supercritical fluid (for example, at point A). When this supercritical fluid is brought to point B or point 0, the solubility decreases and solids precipitate. Since the solutes at points A, B, and C naturally have different compositional ratios, the compositional ratios of the solids precipitated in the process of A-B, A-C, and B→C are also different. For example, between A-8, there is a certain Substance, B→C
In this case, conditions can be set to precipitate a precipitate containing a larger proportion of other specific substances. Figure 3 is a schematic diagram showing a specific example of an apparatus for carrying out hydrothermal synthesis of quartz crystals according to the above principle. It is sealed in a container, and quartz scrap crystals (base material) are placed on the bottom side, and seed crystals are placed on the top side. Then, after sealing the container, it is heated to a supercritical state, and the base material placement area (lower side) is heated to a temperature higher than the critical temperature, while the seed crystal placement area (upper side) is maintained at a lower temperature. The fluid in which a large amount of silica has been dissolved in the base material placement section rises by convection, passes through the baffle, enters the seed crystal placement section, and is gradually cooled there. Silica that becomes supersaturated by cooling precipitates on the seed crystal, and quartz crystal (single crystal) grows there.

By using such a hydrothermal synthesis apparatus, silica single crystals 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 temperature difference is used to extract in the lower part and precipitate in the upper part, so silica is essentially purified, but the time efficiency is low, and sometimes several must be done very gradually over a period of weeks,
For this reason, it has been used only for the synthesis of materials with high industrial added value, such as crystal oscillators. There is also the problem that the relationship between temperature and pressure changes greatly depending on the initial injection ratio of water to the volume of the container, making solubility unstable and making stable synthesis difficult. Such single crystal growth using the supercritical state of water is called hydrothermal synthesis, and is widely used in specific fields.

On the other hand, a supercritical gas extraction process can be cited as a purification technology that utilizes a supercritical state. In other words, the supercritical gas extraction process mainly targets organic mixed systems and is carried out using carbon dioxide, etc., which has a relatively low critical point.
It basically consists of an extraction stage and a separation stage. That is, as can be understood from Fig. 4 showing the basic flow, a supercritical gas solvent and a raw material mixture are introduced into an extraction section, a specific component is extracted from the raw material mixture by the solvent, and then the extraction solvent is sent to a separation section. Here, the specific component is separated from the extraction solvent by expanding it under reduced pressure, and the gasified solvent separated from the specific component is either discharged out of the system as it is or is circulated to the extraction section after being compressed.

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

[Problems to be solved by the invention] As mentioned above, the hydrothermal synthesis process is adaptable to inorganic substances such as silica, but there has been no example of it being used industrially for minute purification. On the other hand, although the supercritical gas extraction process has excellent separation efficiency, it lacks applicability to inorganic substances such as silica, and this apparatus is difficult to apply to the treatment of inorganic substances in the supercritical state of water.

The present invention has been developed in view of these circumstances, and makes it possible to efficiently separate and purify mainly inorganic substances by utilizing the supercritical state of a normally liquid medium, while reducing the energy consumption required for separation. It is an object of the present invention to provide a specific component separation device that can perform supercritical separation efficiently and quickly with a small amount of equipment.

[Means for Solving the Problems] The present invention provides a pressurized supply section that can supply a liquid solvent under pressure above a critical pressure; a high-temperature, high-pressure section capable of maintaining the supercritical fluid at or above its critical temperature and critical pressure; a pressure adjustment mechanism that operates the pressurized supply section to prevent a drop in pressure when the supercritical fluid flows out from the high-temperature, high-pressure section; The main feature is that the recovery part is connected to the outlet of the high-pressure part and is controlled to a lower temperature and/or pressure than the high-temperature and high-pressure part.

[Function] The function of the apparatus of the present invention will be explained below by taking up the case where it is applied to the purification and separation of inorganic substances such as silica, but this does not limit the scope of application of the present invention.

A liquid solvent such as water or an alkaline aqueous solution (hereinafter referred to as an aqueous solvent) is used as an extraction solvent for an inorganic substance such as silica, and the pH can be adjusted as desired depending on the target substance. As mentioned above, an aqueous solvent placed in a supercritical state exhibits excellent extractability for inorganic substances. Therefore, an aqueous solvent that has been heated and pressurized to a supercritical state is made to coexist with the raw material mixture containing the above-mentioned inorganic substance, which is the target substance, to sufficiently dissolve and extract the target substance in the raw material mixture, and this extraction solvent is sent to the separation section. When pumped, depressurized and/or cooled, the solvent (gas or liquid)
Since the inorganic substance serving as the solute solidifies and precipitates, the target substance can be separated. By the way, when using carbon dioxide etc. as an extraction solvent, the critical point of carbon dioxide (critical temperature: 33
．． 1℃, critical pressure (73 atm) is relatively low, so it does not require much energy to heat and pressurize the solvent to a supercritical state.In particular, since the critical temperature is close to room temperature and the critical pressure is low, the extraction section Even if a commercially available high-pressure gas cylinder (150 atm) was used to supply the solvent, a sufficient supercritical state could be 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 quite high as mentioned above, so it takes a certain amount of ability to supply the supercritical solvent to the extraction section and extract this solvent at a predetermined pressure. A compressor with If the solvent to be compressed is a gaseous substance such as carbon dioxide, it is necessary to perform a large compression work, resulting in a considerable amount of energy consumption. On the other hand, when the object to be compressed is a liquid, a large compression work can be performed even with a small amount of power. In this respect, since the aqueous solvent used in the present invention is a liquid at normal temperature and normal pressure, it is sufficient to compress the liquid using a compressor, which has the advantage that the energy consumption for compression is extremely small. The solvent separated from the target substance in the recovery section may be discharged as is, but since it contains some unrecovered target substance, it may be pressurized again and circulated to the extraction section. In this case, since the recovered solvent becomes a liquid when returned to near normal temperature and pressure, it is sufficient to perform liquid compression in a compressor in the same way as with new solvents, and the advantage of reducing compression energy can be obtained.

The apparatus of the present invention is a specific component separation apparatus configured to perform supercritical extraction using an aqueous solvent as an extraction solvent, as shown in the above configuration. It is made up of the main elements.

The pressurizing supply section is a pressure increasing section that pressurizes the aqueous solvent, which is a liquid before compression, above the critical pressure and supplies it to the high temperature and high pressure section. ) means pressurization to a predetermined pressure that can maintain a supercritical state. There are no particular restrictions on the pressurizing means, but preferably a pressure booster or a water pressure pump can be used. The high temperature and high pressure section is a section that receives and holds the pressurized solvent from the pressurized supply section, and the extraction solvent is maintained in a supercritical state within the high pressure chamber of the high temperature and high pressure section.

In order for the solvent that has been pressurized to exceed the critical pressure in the pressurized supply section to reach a supercritical state, the solvent must be heated until it exceeds the critical temperature. Alternatively, it may be carried out during the process from the pressurized supply section to the high-temperature and high-pressure container, or both may be used in combination. External heating and internal heating methods can be considered for heating in high-temperature, high-pressure vessels, but in order to maintain the specified supercritical state without wasting energy, appropriate temperature control is required, so An internal heating method that directly heats the solvent in the container is preferable to an external heating method that heats the solvent via a heating device, and it is desirable to incorporate a heating means within the high pressure chamber of the high temperature and high pressure container. The high-temperature, high-pressure vessel is provided with an outlet for continuously discharging the high-pressure solvent received from the pressurized supply section while maintaining it in a supercritical state. The apparatus of the present invention extracts a target substance from a raw material mixture in such a high-temperature, high-pressure container.Therefore, the high-temperature, high-pressure container is equipped with an inlet for batchwise input of the raw material mixture or a slurry-like raw material mixture. An injection line is provided for continuous injection into the high temperature and high pressure vessel. The next recovery section is a part that receives the supercritical solvent from which the target substance has been extracted in a high-temperature, high-pressure container, and separates and recovers the target substance from the supercritical solvent. Since it is necessary to adjust the temperature and/or pressure to a lower temperature and/or pressure than the recovery section, a mechanism for performing such temperature control or pressure control is attached to the recovery section. However, the method of reducing only the temperature while maintaining the same pressure as the high temperature and high pressure section requires the recovery section to have the same pressure resistance as the high temperature and high pressure section, and it is also necessary to dissipate heat. The equipment burden increases. However, heat dissipation can be substantially achieved using piping 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 actively lowering the pressure to a predetermined pressure. An example of such a pressure-controlled recovery section is a recovery section connected to a back pressure applying device, and a device in which the back pressure applying device itself is a variable capacity high pressure container, and this container is used as the recovery section. But that's fine. The recovery section may be formed of a single container, but may also be formed of two or more containers arranged in parallel. In this case, it is possible to switch between uses, such as taking out collected materials from the other while one is operating. Furthermore, although the above explanation has been based on the assumption that only one type of target substance is to be extracted, it is also possible to extract two or more types of target substances from a raw material mixture. By sequentially introducing the supercritical solvent into the recovery section where the separation temperature and pressure conditions are gradually lowered, the target substances can be separated and recovered from each other due to the difference in solubility of each target substance in the solvent. It is effective to form a recovery section by arranging two or more recovery containers with different pressure and temperature conditions in series.

Note that the back pressure applying device is not limited to a variable capacity high pressure container, but may also be an orifice, a throttle valve, etc., and may be used to control the flow rate. For example, if an orifice is provided at the outlet and outlet of the recovery section, the recovery section is maintained at a lower temperature and pressure than 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 section may be discarded, but it may also be fed to the pressurized supply section again, pressurized to a critical pressure or higher, and then supplied to the high temperature and high pressure section. In this case, as mentioned earlier, the extraction solvent used in the present invention is an aqueous solvent, and the solvent to be supplied is in a liquid state, so if the temperature and pressure are appropriate below the supercritical point, it can be re-pressurized as a liquid. It can be supplied to the liquid supply section.

[Example] Fig. 1 is a schematic diagram showing a specific component separation apparatus according to the present invention, in which 1 shows a pressure intensifier, 2 shows a high temperature and high pressure container, 3a and 3b show a recovery container, and 4 shows a back pressure applying device.

The high-temperature and high-pressure container 2 is formed of a pressure-resistant container 6 with a lid 5 that can withstand high temperatures and high pressures higher than the critical point of water, a filter F is disposed inside the container, and a heater B is built in the bottom of the container 2. Furthermore, a heater A is also arranged around the outer periphery of the container 2. A high-pressure solvent inlet 9 is provided at the bottom of the pressure vessel 6, and a supercritical solvent outlet 10 is provided at the lid 5. On the other hand, the containers 3a and 3b have solvent inlets 11 and 12 at the top and solvent outlets 13 and 14 at the bottom, respectively, and the collection containers 3a and 3b
are connected in series, and the downstream recovery container 3b and the cylinder part 7 of the back pressure applying device 4 are connected by a line fL3. The cylinder part 8 of the pressure intensifier 1 and the high-pressure solvent inlet 9 of the high-temperature and high-pressure vessel 2 are connected by a line f, and the supercritical solvent outlet 10 of the high-temperature and high-pressure vessel 2 and the solvent inlet of the recovery vessel 3a are connected. Mouth 11. is communicated on line 12, and line f1
A heater C and a heater D are provided along the lines at 1° 12, respectively. Also, the discharge line has orifice R1,
R2 and R3 are provided and act as resistance to the flow of the solvent, causing the pressure to sequentially decrease.

In such a specific component separation device, after opening the lid 5 and introducing the raw material mixture M into the high-temperature and high-pressure container 2 and sealing the container airtight, water pumped up from the storage tank T is passed through the line 11. It is introduced into the high-temperature and high-pressure container 2 via the air.

While passing through the line 11, the water is pressurized by the pressure booster 1 to a pressure exceeding the critical pressure, and is heated by the heater C to a considerably high temperature. The high-temperature, high-pressure water introduced into the high-temperature, high-pressure container 2 is supplied to an external heater A installed in the high-temperature, high-pressure container 2.
The water is further heated by the internal heater B, exceeding the critical point of water, and becomes a supercritical fluid. In the high-temperature, high-pressure container 2, the raw material and the supercritical fluid come into contact with each other, 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 β2.

Here, the recovery containers 3a and 3b are connected to a part of the cylinder of the back pressure applying device 4 as described above, and the internal pressure is adjusted by moving the piston of the back pressure applying device 4 back and forth. Incidentally, a back pressure may be applied by an orifice or a throttle valve R3, etc., and the solvent may finally be collected into the container T2. Also, a collection container 3a,
External heaters El and E2 are provided in 3b to adjust the temperature. However, the lever heater can be omitted depending on the nature of the target substance and the pressure of the container of the recovery container, or cooling may be required. The high-temperature, high-pressure water that passes through the line 12 is sequentially introduced into the collection containers 3a and 3b, which are controlled at a predetermined temperature and pressure in this way, and the target substances are separated and separated into the collection containers 3a and 3b, respectively.
Precipitate. In addition, the temperature and pressure at this time are as follows:
It is sufficient to set T r > T 2 and/or p, > R2 between the collection container 3a and the collection container 3a, and set T 2 > T s and/or R2 > R3 between the collection container 3a and the collection container 3b. Or, the target substance is separated and precipitated from the liquid aqueous solvent. Then, water or steam with an extremely low target substance content is discharged from the recovery container 3b, and is stored in the tank T2 via the line 13. After the water or steam in the tank T2 is cooled or pressurized to become steam-free water, it can be recycled to the pressure booster 1 and used for circulation.

In FIG. 1, pressure regulators p and c are provided. This maintains the internal pressure of the high-pressure, high-temperature section at a predetermined value, preventing the pressure from dropping due to the outflow of supercritical fluid.
Alternatively, it prevents excessive pressure from rising.When the pressure intensifier is used as a pressure supply device, a hydraulic pressure adjustment device is used to supply the pressure to the pressure intensifier, and when a pump is used, a relief valve is used. , the pressure supply device may be electrically controlled.

In addition, in the apparatus of the present invention, in order to achieve the pressure conditions of PL>R2 and R2>P, a pressure reducer RI + is installed in the transfer line.
R2 is provided, and the pressure control is performed by a combination of the back pressure applying device and the pressure reducer, but it is of course possible to control the pressure using either one.

In addition, in the above device, an internal heating type heater B is disposed inside the high temperature and high pressure container 2, but since the heater B is exposed to a high temperature and high pressure atmosphere, it is necessary to avoid electrical leakage due to contact with water, steam, etc. inside the container. The heater must have a sealing structure sufficient for this purpose, such as a sheath type heater. Furthermore, if the contents are acidic or alkaline, the sheath tube itself may dissolve or corrode, so it is necessary to use a sheath tube that has appropriate corrosion resistance depending on the contents. Furthermore, it is also possible to arbitrarily determine the temperature distribution in the vertical direction by arranging the internal heaters in an axially divided manner into an upper stage, a middle stage, and a lower stage.

In addition, when high-temperature and high-pressure fluid is caused to flow out from the high-temperature and high-pressure container 2 to the recovery containers 3a and 3b, the fluid may be cooled in the transfer line and the target substance may be precipitated in the line. In particular, if the fluid is allowed to flow out at high speed, internal energy will be converted to kinetic energy, which will lower the fluid temperature and cause precipitation. As a result, the feed line or pressure reducer may become clogged with deposits. To prevent this, the above device is equipped with an external heater D in the transfer line λ2 to cool and cool the target substance.
Heating is done to prevent precipitation. It is more preferable that the heater is an internal heating type heater.

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

(1) Inorganic substances 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 recycled, compression efficiency is high and energy consumption can be reduced compared to systems that require gas compression. That is, operating costs can be reduced.

[Brief explanation of the drawing]

Figure 1 is a schematic diagram showing the specific component separation device of the present invention, Figure 2 is a schematic diagram showing the specific component separation device of the present invention.
The figure is a graph showing the change in solubility of the 5i02-H2O system.
The figure is an explanatory diagram showing a crystal hydrothermal synthesis apparatus, and FIG. 4 is an explanatory diagram showing the basic flow of a supercritical gas extraction process. 1... Pressure booster 2... High temperature and high pressure container 3a,
3b... Recovery container 4... Back pressure applying device ANE・
··heater

Claims (6)

[Claims] (1) A pressurized supply section that can pressurize and supply a liquid solvent above the critical pressure; it is connected to the liquid solvent outlet of the pressurized supply section, and is capable of maintaining the inside at a temperature above the critical temperature and critical pressure. High-temperature and high-pressure section; a pressure adjustment mechanism that operates the pressurized supply section to prevent a decrease in pressure when the supercritical fluid flows out from the high-temperature and high-pressure section; 1. A specific component separation device comprising a recovery section controlled at low temperature and/or pressure. (2) The specific component separation device according to claim 1, wherein the recovery section 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 sections are provided in series or in parallel. (4) The specific component separation device according to claim 2 or 3, wherein the back pressure applying device is a high-pressure container including a variable-capacity high-pressure chamber, and the variable-capacity high-pressure section is a recovery section. (5) The specific component separation device according to any one of claims 1 to 4, wherein the pressure drop in the high temperature and high pressure section is compensated for by the operation of the pressurized supply section. (6) The specific component separation device according to any one of claims 1 to 5, wherein a heater is built in the high pressure chamber of the high temperature and high pressure section.