DK161432B - PROCEDURE FOR EXTRACING FORM LABEL, FLUID MASSES AND MIXING APPLIANCES FOR USING THE PROCEDURE - Google Patents

Abstract

1. Process for the extraction of form-labile, flowable masses by means of high pressure extraction with a liquefied or supercritical gas, characterised in that one conveys the flowable mass and the extraction gas to a mixing chamber , the length of which is a multiple of its breadth or of its diameter and which does not have stirring means, at one end with thorough mixing up and removes from the opposite end, separates the extract-containing gas in a separation step by lowering the density and removes extract and raffinate.

Description

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The invention relates to a method for extracting mold-labile, sound masses by means of high-pressure extraction and an apparatus for carrying out the process.

High-pressure extraction is a process for separating 5 substances in which a substrate is treated with a gas-solvent, which is densified by pressure. The gas is hereby corresponding to its phase diagram in the droplet or overcritical state and is characterized herein by favorable, depending on the set pressure and temperature conditions, more or less selective dissolution properties and mass transport properties. The favorable dissolution behavior of such densified gases has long been known, but the industrial application is still only at a developmental stage and is limited to a few examples, e.g.

15 for removing caffeine from raw coffee and extracting hops.

The advantages of the high-pressure process, especially when using carbon dioxide (CO 2) as a solvent, compared to the classical extraction methods with gasoline fractions or chlorinated hydrocarbons, are sufficiently known: CO 2 is not flammable, is available in large quantities, is physiologically harmless , can be easily and completely separated from extract and refinate and does not cause any environmental problems. In optimum execution of the process, valuable products are immediately obtained which completely or partially eliminate subsequent refining steps and purification steps. This saves energy and costs on the process and avoids dust loss by refining. The high pressure method is therefore a valuable alternative to the usual extraction methods.

Methods are already known in which the extraction of constituents from natural raw materials by the use of condensed gases in liquid or supercritical state. Thus according to DE-PS 21 27 611 spice extracts are extracted from broken or crushed vegetable extract.

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once material. DE-PS 27 09 033 discloses a process for extracting chamomile with supercritical gases and DE-OS 21 27 596 a process for extracting vegetable oils in which the fat is extracted with supercritical gases, preferably from seeds as raw material. Common to these and other methods is that the constituents are extracted from a decomposed raw material of solid or mold stable consistency and larger surface area. The raw material is first placed in an extraction vessel, and the constituents are then dissolved and transported further by the flow-through densified gas upon percolation. DE-PS 14 93 190 discloses a process for separating liquid and / or solid mixtures by means of supercritical gases. The extraction of liquid substance mixtures is thereby effected by contacting the liquid in a mixing step of the type 15 with a column of filler bodies with the supercritical gas, thereby absorbing it in whole or in part. Another embodiment is that a certain amount of the liquid substance to be separated is first placed in the apparatus and the gaseous phase for charge is passed in bubble form through the liquid. Unlimited increases in the liquid phase should be prevented, if necessary, by special measures. DE-AS 23 32 038 discloses a process for deodorizing fatty oils by contacting them with countercritical gas countercurrent using a column of filler bodies. DE-OS 28 43 490 also discloses a process for treating crude vegetable fat oils in which the gas is pumped into the bottom and the material mixture at the top of the extraction autoclave.

To date, no suitable method has been known which allows the use of high pressure extraction for viscous media, rigid pastes or tough masses held together by strong internal cohesive forces.

The difficulty of extracting liquid or viscous, non-stable media consists in providing large infusions.

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dry surfaces. For this purpose, a certain amount of kinetic energy must be provided which serves to overcome the surface energy of the medium used. With thin fluid media with relatively low cohesive forces, 5 under certain circumstances, the potential energy of the inserted medium itself is sufficient to supply it, when flowing into a column of filler bodies, to provide it with a large surface energy needed.

However, this method is only suitable in cases where substrate and raffinate have a sufficient liquid consistency.

If the surface produced is not sufficient and the column gasket is not tight enough, there is a danger that the gas will flow past the liquid film without being charged to the maximum possible equilibrium concentration. A mere and bare passage of the extraction gas through the medium used is also not universally applicable and only of poor efficiency. Application of mechanical movement energy in the form of mechanical movement of the substrate, e.g. with a stirrer, the disadvantage is that such measures under pressure on a technical scale are very cost-intensive and maintenance-intensive, impose many limitations, e.g. with regard to rpm and possible extraction pressure, etc., and that a consequent mechanical transfer of the inserted mixture into the separation part of the plant must be prevented by special measures.

It is the object of the present invention to provide a method for extracting moldable, liquid masses which do not have the disadvantages mentioned above and which are also well suited for extraction of viscous and tough substrates held together by strong inner 30 cohesive forces. This task is solved by the method according to the invention.

BACKGROUND OF THE INVENTION 1. Field of the Invention This invention relates to a process for extracting form-labile, liquid masses with a vaporized or supercritical gas, which is characterized by adding the

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the mass and extraction gas of a mixing chamber, the length of which is several times its width and its diameter, respectively, and having no agitator, at one end under thorough mixing and withdrawing it at the opposite other end, the extract-containing gas mixes in a separation steps by reducing the density and extracting the extract and raffinate.

The form-labile, liquid masses can e.g. are present as molecular dispersion mixture (solution), emulsion or dispersion of various components, single components 10 may be gaseous, liquid or solid, or extract or raffinate may exhibit solid or liquid consistency. The high-pressure extraction according to the invention thus serves to separate desired or undesirable constituents of the inserted substrate in the form of a recovery of a carrier 15 or an extract or a combination of both options.

The inserted mixture may further consist of a liquid dispersion, i.e. of a larger or smaller amount of finely divided solid particles which are retained by adhesive forces in a liquid or viscous matrix. In addition, liquids 20 can also be extracted in a significantly more efficient manner by the process of the invention than in accordance with the prior art, as are solids which, as a dust-gas mixture, can exhibit a flowable behavior. The consistency of the inserted mixture may be changed within certain limits by setting a determined temperature. The temperature in question is independent of the temperature of the extraction gas in the charge step and is limited only by the solidification point of the inserted material and its thermal durability.

It has been found that it is advantageous to utilize the pressure of the extraction gas itself to supply the kinetic energy needed to generate a larger surface, passing the extraction gas and the inserted mixture through a mixing chamber, i.e. performs the charge in a mixing chamber.

Thus, as a mixing chamber, an apparatus suitable for such purposes is used which has appropriate supply lines for the inserted mixture and the extract gas and an output line for 5

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the components after the extraction. For a sufficient extraction, the length of the mixing chamber is conveniently several times the width or diameter of the mixing chamber, the supply of the inserted mixture and the extraction gas being at one end and the outlet at the opposite end of the mixing chamber. Preferably, the inserted mixture (substrate) and / or the extraction gas are introduced into the mixing chamber through nozzles. In one embodiment, the flow direction of the extraction gas at the entrance to the mixing chamber may be substantially perpendicular to the flow direction of the inserted mixture.

Quite particularly good results are obtained with another embodiment in which the inserted mixture and the extraction gas are passed through each of two concentrically arranged as a double mixing nozzle and partially interposed nozzles, e.g.

two stainless steel capillaries. This structure is further elucidated in connection with Figures 1 and 2. Such a device generally achieves better results than with a mixing chamber by which only the inserted medium is injected into the gas phase or only the extraction gas is injected into the liquid mixture.

By means of the preferred device according to the invention, the pressure of the extraction gas is converted to velocity, i.e. kinetic energy. The velocity increase conditioned by the cross-sectional narrowing of the flow-condensed gas phase corresponds to a pressure drop thereof, which, depending on the design of the nozzle, constitutes a larger or smaller size. Accordingly, for the extraction, the pressure produced by the condenser is reduced and this size is reduced by the condensed gas phase. This pressure drop is usually of minor importance compared to the high extraction pressures used and may even, as shown in connection with FIG. 3 is sensibly utilized in a particular embodiment of the method.

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The liquid substrate is supplied through the small inner diameter capillaries 1. Hereby, it has been found that viscous media can be readily pressed through capillaries of only 200 µm inner diameter at appropriate temporal mass in 5 passages. The exact sizing of the capillaries is directed at different points of view and may, depending on the case in question, be different. Above the outlet end of this substrate nozzle is inserted a second capillary 2 concentric, the inner diameter of which is only slightly larger than the outer diameter of the capillary 1, so that over a certain distance, preferably not less than 0.3 cm, and especially 0.5 - 2 cm, is an overlap of the two capillaries. The extraction gas is now supplied in such a way that it must flow through the narrow annular space thus formed between the inner wall of the outer and the outer wall of the inner capillary tube, thereby producing high velocities.

At the point where the inner substrate-bearing nozzle ends, strong eddy formation occurs with irregularly distributed velocity profile. Thereby the mass which is extracted is finely divided and flushed on all sides, which is done automatically by the occurrence of turbulence in the flow. Due to the intensive mixing and the associated high dissolution rate, the gas-substrate mixture can, after a short extraction stretch within the capillary 2, be fed directly into a high-pressure container in which the dissolved raffinate is not collected, while extracted gas phase is passed to the separation part of the plant.

The length of the extraction stretch depends primarily on the velocity of the inserted mixture and the speed and pressure of the extraction gas, on the diameter of the nozzles and, in the case of a double mixing nozzle, on the relationship between the diameters, and furthermore on the nature of the inserted mixture. and the extraction gas. Preferably, the length of the extraction stretch is 3 cm and especially 6-10 cm.

35 The secretion part is effected in a manner known per se

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7 separating the dissolved extract by reducing the density of the extractant. The regenerated gas is then brought back to the desired extraction state by condensation and thermostatification, and can be returned again as in a circular process.

In the preferred embodiment of the invention, the large surface required for effective extraction of the liquid substrate is obtained by a first step or step by combination of two complementary mechanisms of action (first and second steps). The first step for surface enhancement of the mold labile mass is to push it through a fine capillary to give a filamentous structure. The filamentous mass is then, in a second step, decomposed into very small segments of the turbulence occurring in the 15 outer capillary in the rapidly flowing gas, whereupon a mixture of the mass particles with fresh extractant is obtained, whereby a very efficient uniform good extraction can be obtained. without the aid of mechanically moving apparatus parts.

BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 shows a mixer for use in the method according to the invention; FIG. 2 shows the nozzles of the mixer on a larger scale; and FIG. 3 shows an extraction system for carrying out the method according to the invention.

The FIG. 1, a possible embodiment of the mixer according to the invention is preferably used, which has proved suitable in a pilot plant and serves the purpose of illustrating the principle operation of the method 30 according to the invention. In FIG. 1 is denoted by 1 nozzle, where-

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8 easy substrate flows. 2 is a nozzle shot over the nozzle 1 and partially overlaps it, through which the extraction gas enters. FIG. 2 shows a larger detail production of the nozzles (capillaries) 1 and 2. The inner diameter 5 of the nozzle 1 is usually 100-1000 µm, especially 100-400 µm. The inner diameter of the nozzle 2 is generally only slightly larger than the outer diameter of the nozzle 1. It is preferably 250 - 1200 µm and especially 250 - 700 µm. The stretch of road over which the two nozzles 1 and 2 overlap is intended for partial cross-sectional 10 to translate the pressure of the extraction gas partially to velocity, i.e. kinetic energy. As a rule, the overlap distance, which should be as small as possible, is 0.3-4 cm, especially 0.5-2 cm. The cross-sectional narrowing is particularly crucial for the resulting conversion of pressure into motion energy.

In another embodiment, many such nozzles may advantageously be arranged in parallel. A single realization with a single central gas supply can e.g. It is envisaged that the function of the nozzle 2 is taken over by a solid hollow plate with fine parallel bores into which the substrate-carrying fine capillaries 1 are pushed in one piece.

The invention therefore also relates to a mixer of the kind described above for use in the extraction process according to the invention.

FIG. 3 shows, for further illumination, an embodiment of the main part of an extraction system containing the ones in FIG. 1 and 2 as the component and extraction steps as constituent and are suitable for extraction of viscous media. Pressure generation and regulation, including gas supply tank, compressor or pump, control and shut-off valves, etc., are not shown, as these are known measures. In addition, the separation part known per se (one or more steps} in the high-pressure system with connected gas return has been waived.

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From the condenser, the compressed gas enters the system via the shut-off valve VI and exerts here, on the one hand, possibly via a moving piston, a pressure on the substrate to be extracted and contained in a possibly thermostatable autoclave A1. On the other hand, the gas flows via the shut-off valve V2 and the heat exchanger W, which determines the extraction temperature T, into the mixing and extraction steps according to the invention, similar to FIG. 1 and 2, are charged with extractable substances and direct the extract 10 via the pressure vessel A2 and the shut-off valve V5 to the discharge part of the plant. The portion of the substrate which is not soluble in the extractant is referred to as raffinate remains in the pressure vessel A2 and can be withdrawn from it portionwise or continuously via the shut-off valve V4 located below. The autoclave A2 therefore, in some sense, performs the function of a separator, even though the solvent has not been taken up by the solvent.

In carrying out the method, the given pressure is first adjusted in the autoclave A2 by opening valves VI and V2, 20 and then valve V5 is opened and the desired circulation rate of the condensed gas phase is adjusted. The valve V3 is then opened to allow access to the substrate to be extracted in A1. In most cases, the pressure difference caused by the nozzle effect described between A1 and A2, which is dependent on the flow rate of the densified gas, is sufficient to effect the inflow of the viscous mixture. An increased inflow can be effected by incorporating a reduction valve RV according to FIG. 3, by which the slight pressure difference present is further increased. One only has to make sure that the ratio between the applied mass flow of substrate and the applied mass flow of extractant is such that the condensed gas has the ability to dissolve the desired components in accordance with its pressure and temperature conditional absorption. thereby separating them from the inserted mixture.

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As a departure from FIG. 3, the inserted mixture on a technical scale is preferably supplied continuously by means of a metering unit which can be formed as a diaphragm pump or may consist of two long-stroke parallel-injected spindle pumps which are controlled by means of a control such that at any one time one performs the pressure stroke while the other is charged to the next pressure stroke.

By means of the described apparatus, high-pressure extraction of liquid and viscous media or other liquid mixtures is also possible with viscous or solid raffinate phase in a simple manner which, without the use of a mechanical stirrer and the associated investment and operating costs, enables a significantly more efficient mixing and extracting the inserted material with densified gases than was possible with the prior art.

The course of the extraction cannot be compared to the usual ones. high pressure processes which normally require an extraction autoclave and in which the extraction constitutes percolation of the substrate with densified gases as a solvent. These methods therefore have a temporal extraction gradient, e.g. at the beginning of the extraction the gas phase is charged with the more easily soluble substances and towards the end increasingly with parts of heavier soluble components. At the same time, although the maximum possible charge of the gas phase corresponding to the extraction conditions is obtained initially, with increasing depletion of the inserted mixture, the amount of substance in the gas phase decreases and thus the efficiency of the process. This disadvantage is often attempted to offset by the successive insertion of several extraction vessels with different degrees of extraction. In contrast, the method of the invention does not use an extraction autoclave in the usual sense. On the contrary, the charge of the gas phase takes place in a mixing chamber and preferably a small volume section thereof, and especially within or in connection with the double mixing nozzle described. This results in an ex- 11

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traction sequences that can be perceived as temporal order of multiple microextractions of differentially smaller mass portions of the inserted mixture. All microextractions have the same degree of extraction which is dependent only on the state and the solubility of the densified gas phase. There is thus obtained an extract phase which, throughout the extraction process, is qualitatively and quantitatively constant and which always corresponds to the maximum efficiency of the process.

Pressure and temperature in the charge step and also in the excretion step are mainly directed to the evaporated or supercritical gas used for extraction and to the substances to be extracted. Thus, for the extraction of crude lecithin with CO 2, the following conditions are used: In the charging step, preferably at a pressure of 600 - 1200, and in particular 15 from 800 to 1000 bar, and preferably at a temperature of 70 to 150 ° C, especially 80 - 100 ° C. The pressure in the separation step is preferably 40 - 120 bar, especially 40 - 80 bar, and the temperature is preferably 20 - 120 ° C and especially 40 - 80 ° C.

As the extraction gas in the droplet or supercritical state 20, any gas known for high-pressure extraction can generally be used, preferably using gases which are harmless and easy to deal with, which are environmentally friendly, economical and, depending on the nature and use of the refinery and extracts, especially also harmless to health. Preferred gas species according to the invention are alkanes or alkenes having 1-3 carbon atoms, such as e.g. methane, ethane, propane, ethene, their partially or completely fluorinated derivatives, e.g. mono-, di- or trifluoromethane, mono-, di-, tri-, tetra-, penta- or hexafluoroethane, etc., difluoroethylene, tetrafluoroethylene, etc., SFO, argon, nitrogen, and especially carbon dioxide. You can work with a single gas or with a mixture of two or more gases. The gases can be used in supercritical or in the condensed state.

Representative examples of the large number of uses for the extraction process of the invention are to be mentioned: Extraction of Vaseline for Separation of 12

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carcinogenic companion substances, for example, polycondensed aromatic compounds, extraction of wool wax to remove pesticides, polyyelorinated hydrocarbons, allergens, free fatty acids, etc., extraction of lupine oil to remove the toxic quinolizidine alkaloids contained, and especially extraction of crude lithium.

By extracting crude lithium with carbon dioxide as an example, the advantages that can be obtained with the process according to the invention compared with the prior art should be enumerated: a process for the extraction of pure lecithin directly applicable for physiological purposes is known by extraction. with supercritical gases. However, this method is very poor for extractive removal of crude lithium oil and practically impracticable on a technical scale, since the surface of the crude lithine already, at a low degree of extraction, coats with a rubbery layer which prevents any further attack of the supercritical solvent or at least greatly diminishes its effectiveness. In contrast, according to the invention, the extraction of crude lecithin - a case where viscous substrate (crude lecithin), solid raffinate (pure lecithin) and liquid extract (fatty oil) can be carried out quickly, efficiently and completely. According to DE-OS 30 11 185, the extraction with carbon dioxide as extractant is carried out at a pressure in the range 25 72 - 800 bar, preferably 200 - 500 bar and especially 300 - 400 bar, and at temperatures of preferably 35 - 80 ° C, especially 40 ° C. 60 ° C. However, according to the invention, in a pilot plant, complete and rapid extraction of the raw cithin is obtained particularly well in the pressure range from 700 to 1200 bar and at temperatures 30 above 70 ° C. These extraction conditions of the invention not only allow for complete and rapid removal of crude lithium oil, but also have the advantage that, together with the oil, the bulk of the dyes contained, e.g. carotenoids, so that as a raffinate a very light, pure lecithin is obtained in color. The phospholipids themselves are also almost insoluble at the indicated high pressure and temperature values and only as traces contained in the phospholipids.

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intensely dark yellow extracted oil. The higher temperature load does not in any way exert a quality-degrading influence on the resulting pure lecithin, as the elevated temperature acts exclusively under carbon dioxide as a protective gas. Finally, it has been found that by performing high pressure extraction according to the process of the present invention, under the stated conditions, the pure lecithin can be recovered directly in uniform powdery and sprinkling form and therefore both in color and consistency immediately corresponding to the previously known powdered, oil-free pure lecithin or even better than this. The crucial advantage of the process according to the invention is that in a single step, starting from the crude product, an oil-free bright, sprinkling, valuable and directly usable pure product can be obtained immediately. Thus, the many process steps that have been necessary for the removal of oil, purification, removal of solvent residues, drying, pulverization etc. to obtain a comparatively valuable, pure product are avoided by the prior art. Associated with this is a corresponding reduction in the cost of equipment, operation and maintenance thereof (personnel and energy costs) as well as a reduction of substance loss by refining.

In the following examples, the invention is further elucidated. Unless otherwise indicated, the percentages are by weight.

EXAMPLE 1.

Work was done using a pilot system with the one shown in FIG. 1, 2 and 3. The mixer was provided with a substrate nozzle 1 having an inner diameter of 200 µm and an outer diameter of 450 µm. The inner diameter of the nozzle 2 was 600 µm. In the autoclave A1, which was equipped with a movable cylinder but not thermostated and which was at room temperature, 50 g of raw silicon were filled. The heat exchanger W, the double mixing nozzle and the autoclave 14

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friend A2 was set to a temperature of 90 ° C and the extraction pressure of CO 2 to 920 bar. The separation of the extract into its parts was effected in one step at a pressure of 60 bar and a temperature of 60 ° C. After the valve V3 was opened, the addition of the raw lithium occurred within one hour without further action. Upon completion of the addition, the autoclave A2 could be withdrawn approx. 32.5 g of a light, powdery, pure lecithin - while in the excretory part there were about

17.5 g of an almost clear, intensely yellow colored oil. The determination of the amount of lecithin in the extracted oil gave a value of 4%, which was partly dependent on the entrainment effects of the flowing gas in the apparatus used. The oil content of the inserted crude lithium was 35% and could be reduced to a value of only 1.5% through the extraction. A commercially available 15 powdered, refined pure lecithin of high quality has a residual oil content of 2%.

EXAMPLE 2.

The mixer (Figures 1 and 2) was provided with a substrate nozzle 20 1 having an inner diameter of 105 µm and an outer diameter of 200 µm. As nozzle 2, a stainless steel capillary with an internal diameter of 260 µm was selected. The material used was a highly bitter-tasting lupine seed crude oil with a quino-lizidine alkaloids content of 2.8%. First, a well-defined gas circuit was set, with CC> 2 as extractant in the mixing and extraction step exhibiting a pressure of 90 bar and a temperature of 40 ° C. Then, by means of a liquid membrane pump, the lupine oil was dosed into the gas circuit via the substrate nozzle 1. In the mixing step, the oil was then vigorously swirled with extractant so that the contained and, under the chosen conditions, easily soluble free alkaloid bases were taken up in the gas phase and together with a small amount. other oil components transported to the plant's separation tank.

Claims (20)

A process for extracting form-labile, liquefied masses by means of high-pressure extraction with a liquefied or supercritical gas, characterized in that the liquid mass and the extraction gas are fed to a mixing chamber whose length is several times its width 20 and its diameter respectively, and which has no agitator, at one end under thorough mixing and withdrawing it at the opposite other end, the extract-containing gas mixes in a purging step by reducing the density and extracting the extract and raffinate. Process according to claim 1, characterized in that the mixture (substrate) and / or the extraction gas are introduced into the mixing chamber through nozzles. Method according to claim 2, characterized in that the flow direction of the extraction gas at entry into the mixing chamber is perpendicular to the flow direction of the inserted mixture at the entrance to the mixing chamber. DK 161432 B Method according to claim 1, characterized in that the inserted mixture and the extraction gas are introduced through two concentrically arranged, partially superimposed nozzles of different diameters. Process according to claim 4, characterized in that the inserted mixture is introduced through a nozzle (1) into a concentrically injected nozzle (2) which partially overlaps the nozzle (1) through which the nozzle (2) flows in the same direction. . Process according to claims 1-5, characterized in that an intensive mixing of the gas species with the finely divided insert (substrate) takes place in a part on the outlet side of the mixing chamber or mixing nozzle. Process according to claims 1-6, characterized in that the extract and / or the refinate are continuously drawn. Process according to claims 1-7, characterized in that the extraction gas is regenerated and returned to the extraction. Process according to claims 1-8, characterized in that carbon dioxide, alkanes or alkenes having 1-3 carbon atoms, their partially or completely fluorinated derivatives, N 2 O, SF g, argon and / or nitrogen are used as extractants. Process according to claims 1-9, characterized in that the extraction of crude lithium with CO 2 is employed in the loading step at a pressure of 600 '- 1200 bar, in particular 800 - 1000 bar. Process according to claim 10, characterized in that in the loading step, one operates at a temperature of 70 - 150 ° C, especially 80 - 100 ° C. DK 161432 B Process according to claims 1 - 11, characterized in that at the separation stage one operates at a pressure of 40-120 bar, in particular 40 - 80 bar. Process according to claims 1 - 12, characterized in that in the separation step one operates at a temperature of 30 - 120 ° C, especially 40 - 80 ° C. A mixer for use in an extraction process according to claims 1 - 13, consisting of two concentrically arranged, partially overlapping capillaries (1) and (2) of different diameters. Mixer according to claim 14, characterized in that the inner diameter of the inner capillary (1) is 100 - 1000 µm, in particular 100 - 400 µm. Mixer according to claim 14 or 15, characterized in that the inner diameter of the outer capillary (2) is 20 250 - 1200 µm, especially 250 - 700 µm. Mixer according to claims 14 - 16, characterized in that the overlap distance is 0.3-4, especially 0.5-2 cm. Mixing apparatus according to claims 14 - 17, characterized in that the capillary (2) projects 3 - 15, in particular 6 - 10 cm beyond the outlet end of the capillary (1). Mixer according to claims 14 - 18, characterized in that it consists of many parallel overlapping capillaries (1) and (2). Mixing apparatus according to claim 18, characterized in that the parallel capillaries (2) are formed by a hollow plate with parallel bores into which bores the capillaries (1) are inserted.