JPS6328403A - High-pressure carbon dioxide extractor - Google Patents

Abstract

PURPOSE:To obtain the title extractor with improved extraction efficiency by providing a compressor behind a separation vessel wherein the desired components are extracted with high-pressure carbon dioxide and the extract is separated by reducing the pressure, compressing the gaseous carbon dioxide, and then cooling and liquefying the carbon dioxide. CONSTITUTION:The pressure of the liquefied carbon dioxide after extracting the desired components emerging from an extraction vessel 1 is reduced to 50atm which is lower than the critical pressure by a pressure reducing valve 8. Consequently, gaseous carbon dioxide is adiabatically expanded and cooled, and a part of the gas is liquefied. Accordingly, the carbon dioxide is heated by a heating vaporizer 5, gasified, and then supplied to the separation vessel 2. The carbon dioxide separated from the desired components and emerging from the separation vessel 2 is compressed, for example, to 70atm by the compressor 9, supplied to the condenser 6, and cooled and liquefied. The saturation temp. of the carbon dioxide is increased to 28 deg.C by the compression, hence the latent heat of vaporization is decreased, and the amt. of cooling water for the condenser 6 can be reduced. The carbon dioxide liquefied in the condenser 6 is transiently stored in a liquefied carbon dioxide storage tank 3, and then pressurized to the extraction pressure by a pump 7.

Description

DETAILED DESCRIPTION OF THE INVENTION Field of Industrial Application) The present invention relates to a high-pressure carbon dioxide extraction device for extracting target components from raw materials using high-pressure carbon dioxide as an oil agent.

Prior art) Extraction methods using organic solvents as extractants have been used in the food industry, cosmetics, pharmaceuticals, and other fields.

However, this method requires an evaporation operation accompanied by heating to separate the target component from the additive, so it is not suitable when the target component is susceptible to deterioration due to the influence of heat, and the residual organic solvent is harmful to the human body. In such cases, there are disadvantages such as the fact that it cannot be used for foods, etc. Recently, as a method to overcome these drawbacks, a method of using high-pressure carbon dioxide gas as an extractant has been attracting attention. Here, high-pressure carbon dioxide is a general term for liquid carbon dioxide and so-called supercritical carbon dioxide in a state exceeding the critical point (31° C., 73 atmospheres). High-pressure carbon dioxide gas is used in many fields because it has excellent properties as an extractant, such as being able to be extracted at room temperature, being chemically stable, and being harmless to the human body. The following three methods have been proposed for separating and storing the target component extracted by this high-pressure carbon dioxide gas and carbon dioxide gas.

(a) The pressure in the separation tank is appropriately reduced to 1 or less to lower the solubility of the target component in carbon dioxide gas.

(b) The temperature of the separation tank is changed from the temperature of the extraction tank (in many cases, the temperature is raised), and the target component is separated by lowering the drop rate against carbon dioxide (c) Adsorption in the separation tank The target component is adsorbed and separated. Here, the method (b) is not suitable when the target extracted component is easily altered by heat, and the method (c) is not suitable for separating the adsorbent and the target component.
Since there are problems such as the need for operations such as regeneration of the adsorbent, the most commonly used method is (a), in which carbon dioxide gas and the target extraction component are separated by reduced pressure.

The conventional vacuum separation method will be further explained below with reference to FIG. 3 showing the work system. The raw material to be extracted can be charged through the raw material inlet of the extraction tank 1, which is not shown in the drawing. The liquid carbon dioxide in the liquid return storage tank 3 is pressurized to the extraction pressure by the pump 7, preheated to the extraction temperature by the heater &, and continuously supplied to the extraction tank/. In the extraction tank/, the liquid carbon dioxide extracts the target component from the raw material and flows out from the top, after which the pressure is reduced by the pressure reducing valve fK to a pressure that allows the target component and carbon dioxide to be separated. The pressure after this pressure reduction plays an important role; C is a pressure of UO - 0 atm below the critical pressure suitable for sufficient separation. During this depressurization, the temperature of the carbon dioxide gas decreases due to adiabatic expansion, and some of the carbon dioxide gas liquefies, so it is heated in a heating vaporizer, gasified, and then transferred to a separation tank. supply to. In the separation tank 1, the component to be extracted is separated from the carbon dioxide gas and extracted from the bottom of the separation tank 1.

- The carbon dioxide gas is cooled and liquefied in a condenser 6 in order to be reused as an oil agent. During this cooling, the liquefaction temperature of carbon dioxide is t, which is the separation pressure, and the to-ro negative pressure saturation is 5~/j℃, so normal cooling water cannot be used and a refrigerant is used. As the necessary refrigerant, an aqueous solution of ethylene/glycol or propylene glycol is used. The carbon dioxide gas liquefied by cooling in the condenser t is stored in the liquid return storage tank 3, and as described above, is pressurized in the bog-a and recycled as high-pressure carbon dioxide gas for circulation and reuse.

(Problem that the invention seeks to solve) In the conventional vacuum separation method explained above, extractant is used.

All carbon dioxide gas repeats a circulation cycle consisting of the steps of cooling and condensation → pressurization → heating → extraction → adiabatic expansion → heating. Among these processes, the pressure in the cooling and condensing process is influenced by the separation pressure, but at the separation pressure as mentioned above (0-30 atm), the latent heat of vaporization is high due to physical properties, so the amount of cooling heat is large. Because the saturation temperature is as low as 5 to 75 degrees Celsius, normal cooling water cannot be used and a refrigerant must be used, and in order to prepare this refrigerant, it is necessary to install refrigerant generation equipment such as a refrigerator. be. Furthermore, as an operational issue, since the raw materials for extraction are mostly natural, they usually contain water, but if this water migrates into carbon dioxide gas, it creates carbon dioxide hydrates that are difficult to handle. This hydrate is a solid crystal that is produced when carbon dioxide gas containing water is cooled and liquefied under pressure to below 10°C, but when these crystals precipitate, they can cause problems such as clogging of pipes and pump check valves. Conventional solutions to this type of trouble include installing a settler or filter in the liquid carbon dioxide gas line to separate and remove hydrate crystals, or installing a dryer in the carbon dioxide gas line. have been used, but none of them have led to a fundamental solution. The present invention solves the above-mentioned problems of the conventional vacuum separation method, such as the large amount of heat required for cooling and liquefaction during carbon dioxide circulation, the need for a refrigerant and its generation equipment, and the unavoidable formation of hydrates. The object of the present invention is to provide a high-pressure carbon dioxide extraction device that solves the above problems.

Means for Solving the Problems) The present invention has been made in view of the above circumstances, and its gist is to extract target components from raw materials in an extraction tank using high-pressure carbon dioxide gas as an extractant. In a high-pressure carbon dioxide extraction device, the target component is separated from carbon dioxide gas in a separation tank by reducing the pressure, and then cooling and liquefying the carbon dioxide gas in a condenser, increasing the pressure, and circulating it as an extractant. , a high-pressure carbon dioxide extraction apparatus characterized in that a compressor is provided after the separation tank to increase the pressure of carbon dioxide and then cool and liquefy it. As a result of studying the thermodynamic properties of carbon dioxide gas, the present inventor focused on the fact that the closer the saturation pressure is to the critical pressure (73 atmospheres), the lower the latent heat of vaporization becomes, and the higher the saturation temperature becomes. be.

In other words, when the carbon dioxide gas exiting the separation tank is pressurized below the critical pressure, the latent heat of vaporization of the carbon dioxide gas decreases and the saturation temperature increases, so the temperature range is within which it can be cooled and liquefied using normal cooling water, and at the same time, the amount of cooling water can be saved. be. As mentioned above, the carbon dioxide gas leaving the separation tank needs to be pressurized again to the extraction pressure by the pump after being cooled and liquefied, so increasing the pressure before cooling and liquefying is not disadvantageous in terms of the cycle. Another advantage is that when the pressure of the carbon dioxide gas leaving the separation tank is increased using a compressor, the temperature of the carbon dioxide gas increases considerably due to adiabatic compression. By exchanging heat with K, it can be used to heat and vaporize the carbon dioxide gas, which is adiabatically expanded and partially cooled and liquefied. This also has the advantage of reducing the cooling load on the condenser. Another major effect of the present invention is that the cooling liquefaction temperature of the condenser is 20°C.
It is possible to prevent the formation of carbon dioxide-water hydrates, which cause the above-mentioned blockage problem due to the increase in the amount of water, and to fundamentally eliminate this problem.

Embodiment) The content of the present invention will be further explained below based on drawings showing embodiments. FIG. 1 is a work system diagram of the first embodiment. In the figure, the same symbols are used for the same equipment as in the conventional method shown in FIG.

First, an example of Kv, / will be described. The liquid carbon dioxide that extracted the target component exits the extraction tank/reducing valve,! ', the pressure is reduced to a pressure below the critical pressure. During this pressure reduction, the carbon dioxide gas expands adiabatically and the temperature g decreases, so that a part of the carbon dioxide gas is liquefied, so it is heated by a heating vaporizer j, gasified, and then supplied to the portion 11. Separation N! The carbon dioxide gas from which the target extraction components have been separated is pressurized by a compressor 9 to, for example, 70 atmospheres, and then enters a condenser 2 where it is cooled and liquefied. This pressure increase increases the saturation temperature (liquefaction temperature) of carbon dioxide by 2rIQ.
Since the K is increased, it is possible to use normal cooling water, and the latent heat of vaporization is reduced, so the amount of cooling water for the condenser 6 can also be reduced. The carbon dioxide gas liquefied in the condenser B is stored in the liquid coal storage tank JK, and then the extraction pressure is increased to, for example, 300 atm by the pump 7, but as mentioned above, the suction pressure of the pump 7 is as high as 70 atm. The power of the pump 7 decreases proportionally. Furthermore, since the liquefaction temperature in the condenser is 20° C. or higher, the formation of hydrates, which can cause blockage problems, can be prevented.

Next, a second embodiment will be described. Is the liquid carbon dioxide gas, which has extracted all the target components, exiting the extraction tank through a pressure reducing valve? The pressure is reduced to jo pressure, which is below the critical pressure. During this pressure reduction, the carbon dioxide gas expands adiabatically and the temperature drops, so a portion of the carbon dioxide gas liquefies. Separation tank on the other hand! The carbon dioxide gas from which the target extraction components have been separated is pressurized to, for example, 70 atmospheres by a compressor. During this pressure increase, the temperature of carbon dioxide gas increases to an equivalent temperature due to adiabatic compression. Therefore, if the heat exchanger 10 heats the gas exiting the pressure booster valve using the carbon dioxide gas exiting the compressor whose temperature has increased, the amount of heating heat required by the heating vaporizer in the first embodiment can be omitted, and the amount of heat required for the condenser can be omitted. The amount of cooling heat can also be reduced. This embodiment is the same as the first embodiment in that ordinary cooling water can be used in the condenser B, the power of the pump 7 is reduced, and the formation of hydrates can be prevented. Tables 1 and 2 show the results of comparing the amount of utility used by the present invention and the conventional method.

Section/Table Operating conditions) Extraction pressure crab 70 to 9. /c++lG separation pressure crab! O〃 Liquefaction pressure = 70 〃 Extraction @ f: CO fc Carbon dioxide circulation amount: / 000 Kg/Hth λ
Table operating conditions) Extraction pressure crab 300Kg/da Separation pressure crab
10 g Liquefied pressure crab 70 # Extraction temperature: <10℃ Carbon dioxide circulation! : / 000 Kf/H Effects of the Invention) According to the apparatus according to the present invention described above, the following effects not available in conventional apparatuses can be obtained.

(a) Since the liquefaction temperature in the condenser is high and normal cooling water can be used, there is no need to install refrigerant generation equipment.

Port C) The cooling heat loss of the condenser is reduced and cooling water can be saved.

(c) The amount of heat required for heating and vaporizing the gas exiting the pressure reducing valve can be reduced.

(d) Since the formation of carbon dioxide hydrates can be prevented, blockage problems caused by this can be eliminated.

[Brief explanation of the drawing]

1 and 2 are work system diagrams of the embodiment of the present invention, and 3.
The figure is a work flow diagram of a conventional device. 1: Extraction tank, Koni separation tank, 3: Liquid return storage tank, 1: Heater,
! : heating vaporizer, t: condenser, 7: pump, r: pressure reducing valve, ri: compressor, lO: heat exchanger.

Claims (1)

[Claims] After extracting the target component in the raw material in an extraction tank using high-pressure carbon dioxide gas as an extraction agent, the pressure is reduced and the target component is separated from the carbon dioxide gas in a separation tank.The carbon dioxide gas is then cooled and liquefied in a condenser. 1. A high-pressure carbon dioxide extraction device which pressurizes the carbon dioxide gas and recirculates it as an extraction agent, wherein a compressor is provided after the separation tank to pressurize the carbon dioxide gas and then cool and liquefy it.