JPH047733B2 - - Google Patents

Description

[Detailed description of the invention]

INDUSTRIAL APPLICATION FIELD The present invention relates to a method for separating a purified product mainly consisting of an organic liquid solute from a solution containing the same solute, and more specifically, to a method for separating a purified product mainly consisting of an organic liquid solute, using an extraction solvent fluid that is near a critical point or in a supercritical state. It concerns a method of performing the separation. Throughout this specification, the term "solvent fluid" refers to a fluid that is mainly composed of a solvent that has an extractive action, and may also contain an organic liquid solute, a raw solvent, and/or impurities, and that is in a near-critical or supercritical state. A liquid or gaseous mixture, "raw solvent" refers to the liquid component that dissolved the solute prior to solvent extraction, and a "supercritical" state refers to the temperature and/or This refers to the state in which the pressure exceeds its critical point. In addition, % indicating a ratio is calculated on a weight basis. Conventional technology and its problems Conventionally, distillation has been commonly used to separate and obtain organic liquid solutes from aqueous solutions or organic solvent solutions, but distillation requires a large amount of energy. Therefore, there is a need for a method that can separate and obtain the solute with less energy. From this point of view, there is a technology in which a solution containing an organic liquid solute is brought into contact with a solvent fluid near a critical point or in a supercritical state, and the same liquid quality is extracted from the solution into a solvent fluid, and the same liquid quality is separated. It is known (Japanese Patent Publication No. 10539/1983 and Japanese Patent Application Laid-open No. 56201/1983). In the method disclosed in Japanese Unexamined Patent Publication No. 56-56201, as shown in FIG. 4, the following operations are performed. That is, a solution containing an organic liquid solute, a raw solvent, and/or impurities is supplied by a pump 51 to the top of an extractor 53 via a heat exchanger 52, where the solvent fluid in a near critical point or supercritical state is extracted. The solute is transferred from the solution to the solvent fluid.
Then, a crude extract consisting of a solvent fluid with increased solute content is sent from the top of the extractor 53 to a distillation column 55 via a pressure reducing valve 54, and by distilling the crude extract, a purified product mainly consisting of solutes is obtained at the bottom of the column. It is extracted from the valve 56 through the valve 56. Further, the regenerated solvent fluid recovered from the top of the distillation column 55 is pressurized by the compressor 57, and the pressurized fluid is transferred to the reboiler 58 of the distillation column 55 and the heat exchanger 59.
It is passed through and returned to the extractor 53 for reuse. The extraction residue, consisting of the solution whose solute content has been reduced by the extraction in the extractor 53, is drawn off from the bottom via the valve 60. By the way, when a solvent fluid near a critical point or in a supercritical state is used to extract an organic liquid solute from a solution containing an original solvent and/or impurities, the following constant phenomenon occurs. That is, in general, the solubility of a substance in a solvent increases as the density of the solvent increases, so as the temperature increases under a constant pressure, the density of the solvent decreases, resulting in the solubility of the solute, base solvent and /or the solubility of impurities tends to decrease. On the other hand, since the vapor pressure of solutes, raw solvents and/or impurities in a solvent generally increases as the temperature increases, the solubility of these substances also tends to increase. Therefore, the solubility of a solute, parent solvent and/or impurity in a solvent increases with increasing temperature, depending on which of the density of the solvent and the vapor pressure of the solute are more influential at a constant pressure. It can be high or low. In addition, the solubility selectivity of a solute in a solvent with respect to a base solvent and/or impurities changes depending on the tendency of solubility of a solute, a base solvent, and/or an impurity in a solvent with a change in temperature under a constant pressure. As it rises, it also becomes higher and lower. In view of this phenomenon, in the method shown in FIG. 4, it is important to control the extraction temperature in order to obtain a high-quality purified product, and therefore the solution and solvent fluids supplied to the extractor 53 are respectively 52 and a heat exchanger 59, which increased the cost of the product. In addition, in this method, when the extraction temperature to obtain a purified product of desired quality is in a relatively low range, the difference in specific gravity between the solvent and the solution is small, so a multi-column type or packed column type extractor is used. This sometimes made extraction operations difficult. This invention was made in view of the above-mentioned circumstances, and does not require a large amount of energy to obtain a purified product of desired quality, and even when the extraction temperature is in a relatively low temperature range. It is an object of the present invention to provide a method and an apparatus for performing the extraction operation easily. Means for Solving the Problems The method according to the present invention is configured as follows to achieve the above object. That is, the present invention provides a method for separating an organic liquid solute from a solution containing a raw solvent and/or impurities by solvent extraction, by: a) bringing the solution into contact with a solvent fluid near a critical point or in a supercritical state; and extracting the solute from the solution into a solvent fluid to produce a crude extract consisting of a solvent fluid with an increased solute content and an extraction residue consisting of a solution with a decreased solute content. b) The obtained crude extract is adjusted to a required temperature by heat exchange to increase the content of solutes, and the main extraction component consists of the crude extract, and the raw solvent and/or c) heat exchange the obtained extracted main product with the crude extract; d) after heat exchange. The extracted main product is depressurized to produce a purified product mainly consisting of the solute and a solvent fluid mainly composed of the solvent, and the purified product and the solvent fluid are separated to obtain the purified product and recover the regenerated solvent fluid. , a method for separating a solute from an organic liquid solute-containing solution by solvent extraction, characterized by comprising various steps. The pressure in stage a is near the critical pressure of the solvent fluid, or stage a is in the supercritical state of the solvent fluid. Typical examples of solvents are carbon dioxide, ethane, ethylene, propane or propylene. Typical examples of organic liquid solutes are alcohols, aldehydes, esters, ketones, organic acids or fusel oils. Typical examples of alcohols are methanol, ethanol, normal propanol, isopropanol,
Normal butanol, isobutanol, sec-butanol or tertiary-butanol. Representative examples of fusel oils are isopropanol, normal propanol, normal butanol, sec-butanol, tertiary-butanol, isobutanol, isoamyl alcohol, 1-pentanol, 2-pentanol, acetone, methyl ethyl ketone, methyl n-propyl ketone, methyl isobutyl. ketone, n-butyraldehyde, isobutyraldehyde or isopropyl ether, or a mixture thereof. Typical examples of organic acids are acetic acid or butyric acid. Typical examples of aldehydes are acetaldehyde, n
-butyraldehyde, isobutyraldehyde. Representative examples of ketones are methyl ethyl ketone, methyl-n-propyl ketone, and methyl isopropyl ketone. Typical examples of stock solutions are water, methanol, ethanol, isopropanol, normal propanol,
These are normal butanol, sec-butanol, tertiary-butanol, and isobutanol. The solvent is preferably carbon dioxide at a pressure of about 30 to about 200 atmospheres and a temperature of about -10°C to about 150°C;
or a pressure of about 50 to about 200 and a temperature of about -10
℃ to about 150℃. In a preferred embodiment of the invention, following step d), the separated regenerated solvent fluid is compressed and the compressed solvent fluid is reused as the solvent fluid in extraction step a). and in step b),
The heat exchanged crude extract is heat exchanged with the compressed regenerated solvent fluid to impart thermal energy from compression to the crude extract. Also following step c), the extracted mass is heat exchanged with the compressed regenerated solvent fluid to impart thermal energy from compression to the extracted mass. In addition, a distillation column or a stripping column is used as a separation means in step d), and the compressed regenerated solvent fluid is heat exchanged with the bottom liquid of the distillation column or stripping column, and the thermal energy from the compression is transferred to the distillation column or stripping column as a heat source. give as. The by-products separated in step b) are also fed to step a. Also, the extraction residue separated in step a) is heat exchanged with the compressed regenerated solvent fluid to impart thermal energy from the compression to the extraction residue, and the solvent contained in the residue is vaporized and recovered. If the solution is also an aqueous ethanol solution, the by-products separated in step b are fed to a fermentation stage producing an aqueous ethanol solution. A second aspect of the invention is an apparatus for carrying out the method of the first invention, which is a device for carrying out the method of the first invention, wherein a solution containing an organic liquid solute, a raw solvent and/or an impurity is brought to a state near a critical point or in a supercritical state. an extraction means for contacting with a solvent fluid to produce a crude extract consisting of a solvent fluid with an increased solute content and an extraction residue consisting of a solution with a reduced solute content; Temperature adjustment means for adjusting the temperature to a required temperature by exchange to produce an extraction main component consisting of a crude extract with increased solute content and a by-product mainly consisting of the original solvent and/or impurities; a separation means for separating the separated main extraction products and by-products, a heat exchange means for exchanging heat between the separated main extraction products and the crude extract, and a means for reducing the pressure of the main extraction products after the heat exchange. , a depressurizing means for producing a purified product mainly consisting of a solute and a solvent fluid mainly composed of a solvent, and a separation means for separating the obtained purified product and solvent fluid to obtain a purified product and recovering a regenerated solvent fluid. It is characterized by having various means. Effects of the invention Since this invention is configured as described above,
The extraction operation can be carried out at or near ambient temperature and then a vapor-liquid equilibrium condition can be established at the lower temperature. The method of the invention therefore allows for a significant saving in the energy required to obtain a product of the desired quality and in addition to the extraction Even if the temperature is in a relatively low temperature range,
Extraction operations can be easily carried out. Examples Next, examples of the present invention will be shown in order to demonstrate the above effects. Example 1 In FIG. 1, an ethanol aqueous solution in which the organic liquid solute is ethanol and the original solvent is water is supplied by pump 1 to the top of extractor 2, where it is near the critical point or in a supercritical state. Contact with a carbon dioxide-based solvent fluid causes the ethanol to be transferred from the solution to the solvent fluid. A crude extract consisting of a solvent fluid enriched with ethanol is then withdrawn from the top of the extractor 2, and an extraction residue consisting mainly of water is withdrawn from the bottom of the extractor 2 via a valve 3. Here, the extraction operation in the extractor 2 can be carried out at or near ambient temperature, and precise temperature control of the solution and solvent fluids is not required. Next, the obtained crude extract is cooled by passing it through a heat exchanger 4 through which a main extraction product (described later) passes and a first auxiliary heat exchanger 5 through which a refrigerant passes. As a result, the solubility of ethanol in the crude extract decreases slightly and some of the ethanol is condensed. Furthermore, the dissolution selectivity of ethanol to carbon dioxide relative to water becomes high, and most of the water in the crude extract is condensed. In this way, a by-product consisting of a dilute aqueous ethanol solution and a main extraction product consisting of a crude extract with increased ethanol content are produced. Then, the cooled mixture is introduced into the first separator 6 to separate the main extracted product and by-products. The separated by-products are extracted from the first separator 6 through the valve 7. At least a portion of the by-product may be supplied to the extractor 2 together with the ethanol aqueous solution. The by-product may also be fed to a fermentation stage that produces an aqueous ethanol solution. Even when the difference in specific gravity between low-temperature carbon dioxide and by-products is small, separation can be easily achieved using a stationary separator or a coalescing separator. Then, the obtained extraction main product is transferred to the heat exchanger 4.
The crude extract is used as a cooling medium for the crude extract, and is further heated by passing through a second auxiliary heat exchanger 8 through which a compressed solvent fluid, which will be described later, passes. Next, the extracted main product after heat exchange is led to a pressure reducer 9 to reduce the pressure, and a purified product mainly consisting of ethanol is obtained.
A solvent fluid mainly composed of carbon dioxide is produced. Here, the solubility of ethanol in carbon dioxide decreases due to the density change of carbon dioxide accompanying the reduced pressure, and most of the ethanol is liquefied, producing a purified product consisting of highly concentrated ethanol. Then, the mixture after depressurization is transferred to the second separator 10.
The purified product and the solvent fluid are separated, and the purified product is withdrawn from the second separator 10 via the valve 11. In addition, a solvent fluid mainly composed of carbon dioxide is used as a second solvent fluid.
Collected from the separator 10 and guided to the compressor 12,
The compressed solvent fluid is passed through the second auxiliary heat exchanger 8 to be used as a heating source for the extraction main product, and then to the extractor 2 for reuse as the solvent fluid in the extraction stage. Alternatively, the regenerated solvent fluid may be heat exchanged with the extraction residue discharged from the extractor 2 to impart thermal energy through compression to the extraction residue, and the solvent contained in the residue may be vaporized and recovered. Furthermore, the regenerated solvent fluid before being returned to the extractor 2 may be cooled in a third auxiliary heat exchanger 13 through which a refrigerant passes. Comparative Test Regarding the method of Example 1 shown in Figure 1 and the conventional method shown in Figure 4 (atmospheric temperature 25°C, vapor-liquid equilibrium relationship to obtain the required ethanol concentration is 130 atm and 5°C) , and compared the energy consumption. The thermal process of the method of Example 1 is as shown in the Molière diagram of carbon dioxide shown in FIG. Fifth
In the figure, point 21 is the extractor 2, point 22 is the outlet of the heat exchanger 4, point 23 is the first separator 6, and point 24
is the outlet of the second auxiliary heat exchanger 8, and point 25 is the outlet of the pressure reducer 9.
point 26 is the inlet of the second separator 10, point 27 is the outlet of the compressor 12, point 28 is the third auxiliary heat exchanger 1
The states at the exits of No. 3 are shown respectively. The cooling process from point 28 to point 21 is carried out by the first auxiliary heat exchanger 5.
This can also be achieved by increasing the load of the third auxiliary heat exchanger 13, but here it is achieved by the third auxiliary heat exchanger 13. At point 21, the temperature is 25℃, at point 22, the temperature is 10℃, and at point 23
In this case, the temperature is 5°C. On the other hand, the thermal process of the conventional method shown in FIG.
This is the Molière diagram of carbon dioxide shown in the figure. In FIG. 6, point 31 indicates the state at the extractor 53, point 32 at the outlet of the pressure reducer 54, point 33 at the outlet of the distillation column 55, point 34 at the outlet of the compressor 57, and point 35 at the outlet of the reboiler 58, respectively. show. Cooling by the heat exchanger 59 is shown as a cooling process from point 35 to point 31. In the conventional method, it is necessary to maintain the extractor 53 at 5°C, so the temperature at point 31 is 5°C. Although the energy required for the heat exchanger 53 of FIG. 4 is not shown in FIG. 6, it is necessary to cool the temperature of the solution from 25° C. to 5° C. Under such conditions, the energy required for cooling is as follows.

[Table] As is clear from the table above, the method of Example 1 requires less energy than the conventional method.
You can save more than 10%. Also, in reality,
In the conventional method, the solvent fluid is cooled from about 25° C. to 5° C. in the heat exchanger 59, which requires energy-intensive cooling means such as a refrigerator. On the other hand, in the method of Example 1, the third auxiliary heat exchanger 13 cools the solvent fluid from about 35°C to 25°C. It can be done by means. Therefore, in the method of Example 1, the required energy is
180Kcal/・Ethanol is sufficient, which is less than 20% of the amount required using the conventional method. Example 2 In FIG. 2, a distillation column 14 is used as a means for separating the purified product produced by reducing the pressure of the extraction main product and the solvent fluid, and the mixture after the pressure reduction is introduced into the distillation column 14, and the purified product is collected at the bottom of the column. It is extracted through valve 11.
Further, after the solvent fluid is recovered from the top of the column and compressed by the compressor 12, it is passed through the reboiler 15 of the distillation column 14 to exchange heat with the column bottom liquid, and the thermal energy from the compression is used as a heat source for the distillation column 14. The solvent fluid after heat exchange is then returned to the extractor 2. A stripping column may be used instead of a distillation column. The other configurations in FIG. 2 are the same as those in FIG. 1. Example 3 In FIG. 3, the regenerated solvent fluid after compression is passed through the first auxiliary heat exchanger 5 to exchange heat with the crude extract,
Thermal energy from compression is applied to the crude extract to heat it. Further, in this case, the second auxiliary heat exchanger is omitted. This flow is preferably adopted when the solubility of the solute in the solvent decreases as the temperature increases, and conversely, the solubility selectivity of the solute in the solvent with respect to the raw solvent and/or impurities increases. The other configurations in FIG. 3 are the same as those in FIG. 1.

[Brief explanation of drawings]

1, 2, and 3 are step system diagrams showing the flow of Embodiment 1, Embodiment 2, and Embodiment 3, respectively, of the present invention, and FIG. 4 is a step system diagram showing the conventional flow, and FIG. 5 is a Molière diagram for the case of FIG. 1, and FIG. 6 is a Molière diagram for the case of FIG. 4. 1...Pump, 2...Extractor, 3...Valve, 4...
... heat exchanger, 5 ... first auxiliary heat exchanger, 6 ... first separator, 7 ... valve, 8 ... second auxiliary heat exchanger, 9 ... pressure reducing valve, 10 ... second separator, 1
1... Valve, 12... Compressor, 13... Third auxiliary heat exchanger, 14... Distillation column, 15... Reboiler.

Claims (1)

[Claims] 1. In separating an organic liquid solute from a solution containing a raw solvent and/or impurities by solvent extraction, a) the solution is treated as a solvent fluid near a critical point or in a supercritical state; contact to extract the solute from the solution into a solvent fluid, producing a crude extract consisting of the solvent fluid with increased solute content and an extraction residue consisting of the solution with decreased solute content; Separate the extract and the extraction residue, and b) adjust the temperature of the obtained crude extract to the required temperature by heat exchange to obtain the main extraction component consisting of the crude extract with increased solute content, the raw solvent and c) heat exchange the obtained extracted main product with the crude extract; d) heat exchange. The main extracted product is depressurized to produce a purified product mainly consisting of the solute and a solvent fluid mainly composed of the solvent, and the purified product and the solvent fluid are separated to obtain the purified product and a regenerated solvent fluid. A method for separating a solute from an organic liquid solute-containing solution by solvent extraction, the method comprising the steps of recovering the same solute from an organic liquid solute-containing solution. 2. The method of claim 1, wherein the pressure in step a) is near the critical pressure of the solvent fluid. 3. The method of claim 1, wherein step a) is in a supercritical state of the solvent fluid. 4. The method according to claim 1, wherein the solvent is carbon dioxide, ethane, ethylene, propane or propylene. 5. The method according to claim 1, wherein the organic liquid solute is alcohols, aldehydes, esters, ketones, organic acids, or fusel oil. 6. The method according to claim 5, wherein the alcohol is methanol, ethanol, normal propanol, isopropanol, normal butanol, isobutanol, sec-butanol or tertiary-butanol. 7 Fusel oil is isopropanol, normal propanol, normal butanol, sec-butanol, tertiary-butanol, isobutanol, isoamyl alcohol, 1-pentanol, 2-pentanol, acetone, methyl ethyl ketone, methyl n
-propyl ketone, methyl isobutyl ketone, n
-butyraldehyde, isobutyraldehyde or isopropyl ether, or a mixture thereof. 8. The method according to claim 5, wherein the organic acid is acetic acid or butyric acid. 9. The method according to claim 5, wherein the aldehyde is acetaldehyde, n-butyraldehyde, or isobutyraldehyde. 10 Ketones are methyl ethyl ketone, methyl-
The method according to claim 5, wherein n-propyl ketone and methyl isopropyl ketone are used. 11 Claim 1, wherein the stock solution is water, methanol, ethanol, isopropanol, normal propanol, normal butanol, sec-butanol, tertiary-butanol, isobutanol
The method described in section. 12. The method of claim 4, wherein the solvent is carbon dioxide at a pressure of about 30 to about 200 atmospheres and a temperature of about -10C to about 150C. 13 The solvent is at a pressure of about 20 to about 200 atmospheres and a temperature of -
5. The method of claim 4, wherein the ethane is from 10<0>C to about 150<0>C. 14. The method of claim 1, wherein following step d) the separated regenerated solvent fluid is compressed and the compressed solvent fluid is reused as solvent fluid in extraction step a). 15. The method of claim 14, wherein in step b, the heat-exchanged crude extract is heat-exchanged with the compressed regenerated solvent fluid to impart thermal energy from compression to the crude extract. 16. The method of claim 14, wherein following step c), the extraction base is heat exchanged with the compressed regenerated solvent fluid to provide the extraction base with thermal energy due to compression. 17. Using a distillation column or a stripping column as the separation means in step d), the compressed regenerated solvent fluid is heat exchanged with the bottom liquid of the distillation column or stripping column, and the thermal energy from the compression is used as a heat source for the distillation column or stripping column. 15. The method of claim 14, provided as: 18. The method of claim 1, wherein the by-product separated in step b) is fed to step a). 19. Heat exchange the extracted residue separated in step a) with the compressed regenerated solvent fluid to impart thermal energy from compression to the extracted residue and vaporize and recover the solvent contained in the same; A method according to claim 14. 20 The solution is an aqueous ethanol solution and step b)
2. The method of claim 1, wherein the by-products separated in step 1 are fed to a fermentation stage producing an aqueous ethanol solution. 21 A solution containing an organic liquid solute, a raw solvent and/or an impurity is brought into contact with a solvent fluid near a critical point or in a supercritical state to obtain a crude extract consisting of a solvent fluid with an increased solute content, and a crude extract consisting of a solvent fluid with an increased solute content. an extraction means for producing an extraction residue consisting of a reduced solution; and an extraction main product consisting of a crude extract whose solute content is increased by adjusting the temperature of the obtained crude extract to a required temperature by heat exchange. and a by-product mainly consisting of the raw solvent and/or impurities; a separation means for separating the obtained main extracted product and the by-product; a heat exchange means for exchanging heat with the crude extract; a decompression means for reducing the pressure of the extracted main product after heat exchange to produce a purified product mainly consisting of a solute and a solvent fluid mainly consisting of a solvent; separating the same solute from an organic liquid solute-containing solution by solvent extraction, characterized by comprising means for separating the purified product and the solvent fluid to obtain the purified product and recovering the regenerated solvent fluid. Device.