Combined Mobile Unit for Supercritical CO 2 -Extraction of Bio-Active Components

A review and assessment of methods for the extraction of active biocomponents from plant raw materials is presented. The overview contains a tables to facilitate the initial perception of this topic. Examples of stationary and mobile installations developed in the world are described. The prospects of the Super-critical CO 2 -extraction method, as the most effective for the extraction of valuable biomedical components, have been analyzed. The schemes and samples of the used CO 2 -extractors are shown. The technical diagrams and appearance of the author’s experimental supercritical CO 2 extractor were presented. A detailed description of an new-generation of experimental mobile installationwere done, its complete set and the possibilities of supercritical CO 2 -extraction for processing plant raw materials are given. New engineering and technical solutions in the operation of a mechanical system were demonstrated. There includes an improved construction of a high gas-pressure throttle valve installed in storage tanks, and innovations in the system for loading-unloading raw materials using removable nozzles. The operating parameters of the functional elements and their resource are indicated. As a result of successful working, the templates of obtained extracts were presented.


Introduction
General information on methods for extracting active ingredients. The isolation and extraction of juices and oils have been known since pre-historic epoque. A large number of scientific and patent-commercial literature is devoted to extraction methods . Simplistically, they are divided into traditional and new (advanced, innovative, etc, (Table 1) [1][2][3][4][5][6][7][8]. Steam is passed through the raw material, with which valuable substances leave, which are subsequently removed by decantation.
Labor-intensive: to obtain a liter of aromatic oil, ≈100-1000 kg of plant raw materials are required.

Water+alcool extraction
Washing of raw materials with 60-80% alcohol solution, followed by drying.
some of the valuable substances insoluble in alcohol remain in the cake. The need for recycling alcohol. Extraction of extractive substances from oil-bearing materials accompanied by processing pulsed electric field.
Non-thermal and energy-efficient processing of raw materials with high-voltage pulses of short duration and the possibility of destroying the integrity of the surface of plant cell membranes 9 Cryogenic and supercritical (СО 2 -) extraction Crushing of raw materials to powder, in liquid nitrogen (-196°C). Then extraction with compressed CO 2 carbon dioxide under pressure at room temperature (30 ° C). allows you to fully preserve the beneficial properties of the components of plant raw materials

Let's Take a Quick Look at the Same Existing Methods
Cold pressing can be considered one of the oldest and most proven methods. It was used in ancient civilizations. And since then, only the materials of the auxiliary parts have changed (plastic and chrome-plated instead of wooden). It is very effective for easily squeezed plant products.
Hot pressing remains an applied method in the food industry.
Water-steam extraction is still considered the simplest and most effective method. According to Kasyanov [2], "distillation of volatile components with (100°C) allows to extract substances with low boiling point (150-250°C) from plant raw materials. The advantages of the steam distillation method include the availability of its implementation even in field conditions and the low cost of producing essential oils. But at a high temperature of distillation of volatile substances, denaturation and modification of a number of valuable components occurs. In addition, some essential oils require refining due to the presence of decomposition products." The variant of method is a vacuum-distillation, which is more progressive than conventional atmospheric distillation, is used for refining crude oils [6,17].
Extraction with oils. It is relevant to this day, which is confirmed by the emergence of new patents on this topic [3]. The extraction method for extracting oils can be used in pure form (for soybean raw materials), but more often -in combination with prepressing (for high-oilseeds). Direct extraction of high-oil crops is difficult due to the high caking of such materials after grinding. When combining the extraction method with pre-pressing, at the first stage, up to 80-85% of the oil is extracted, which facilitates the second stageextraction. The final products of the extraction are oil and fat-free material -meal [2][3][4][5][6].
Extraction with solvents depends on their polarity. As is known [2], according to polarity, solvents are subdivided into low polarity, medium and high polarity. And almost all vegetable oils dissolve well in non-polar solvents (hexane, gasoline, benzene, dichloroethane, etc.). Polar solvents (methanol, ethanol, isopropanol) are mixed with oils in limited quantities at room temperature; when heated, the solubility of oils in them increases [2]. In the practice of extraction of vegetable oils, the most widespread are aliphatic hydrocarbons -extraction gasolines etc. [2]. When using hydrophilic solvents (acetone, glycerin, ethanol), extracts are obtained that are soluble in water, but contain a significant amount of dyes and other undesirable substances. Hydrophobic solvents (hexane, dichloroethane, СCl4) extract fat-like substances better, but not carbohydrates, resins, gums [2]. When extracting with solvents, the method of drying. New effective methods -micro-wave or vacuum drying, allow maximum preservation of useful substances. These drying methods are used in the production of dietary supplements and fine synthesis products [2]. The disadvantages of solvent extraction are obvious and unavoidable: fire hazard, ecotoxicity (of most solvents), loss of quality of extracts when distilling off the solvent [1,2]. The main disadvantage is that solvent does not always ensure a sufficiently complete extraction of aromatic and flavoring substances from raw materials [2].
Pre-critical extraction. The disadvantages of solvent extraction are eliminated when extracting from plant raw materials with liquefied gases -butane, propane, liquid carbon dioxide, freons, etc. [1][2][3][4][5]. This explains the popularity of pre-critical gas extraction methods. A new method of extracting oils from oilseeds can be used in pure form (for soybean raw materials), but more often -in combination with prepressing (for high-oilseeds). Direct extraction of high-oil crops is difficult due to the high caking of such materials after grinding. When combining the extraction method with prepressing, at the first stage, 80-85% of the oil is extracted, which facilitates the second stage -extraction. The final products of the extraction are oil and fat-free material meal [1,2].
Processing by a pulsed electric field, have next advantages -nonthermal and energy-efficient processing of raw materials by short high-voltage pulses and the possibility of destruction the integrity of the surface of the membranes of plant cells [7]. But this method has not yet found widespread use in the processing of oilseeds, due to insufficient the studied mechanisms of mass transfer, energy calculations and electrical parameters of the processed medium.

Supercritical Extraction Method (SCE)
Super-critical extraction as a method has developed in the last 20 years, replacing traditional methods [1][2][3][4][5][6][7][8]. Supercritical technologies are a promising alternative to many existing technological processes, the functioning of which requires the creation of new equipment and corresponding tooling operating under high pressure [1,2]. In turn, supercritical extraction, with its intensive development, came to replace many traditional methods, displacing them [1][2][3][4][5][6][7][8]. SCFE is based on the property of a gas under the influence of pressure and temperature to pass into a fluid phase, which has the ability to permeate gas and the solubility of  Table 2.
It can be seen from it that it is the SCE method that makes it possible to extract the most difficult to access valuable components. Moreover, its efficiency increases with increasing pressure ( Table   2). The properties of supercritical CO 2 as a solvent can be controlled -with an increase in pressure and temperature, its dissolving capacity increases sharply [2][3][4]. For CO 2 , these parameters are   [7,9,13].

Our Combined Model of Scf-Extractor
Our group has experience in the creation and service of machines,devices and equipment for various fields (Industrial/ geological [22],field equipment [23],prosthetics [24-,25].
Our CO 2 extraction unit includes the following interacting is a given territory. In our scientific arsenal there are developments in processing technologies: seeds of flax, thyme, amaranth, millet, rose hips, and a method for obtaining extracts from plant raw materials has been worked out [21].
The extraction process is determined by the following main indicators: extraction time, temperature and pressure in the extractor, temperature and pressure in two separators, gas phase flow rate.
Development of optimal technological modes of fluid extraction of raw materials is carried out according to such indicators: pressure, temperature, cycle time, rational product yield, flow rate, modulation of CO 2 flow and pressure, optimal humidity, etc.

2)
Original design of an automated CarbEx control system, which allows smoothly regulating the CO 2 consumption, which contributes to a change in the density of the fluid. It let to obtain extracts of various composition and quality, as well as, depending on the type of raw material, and accordingly program the extraction control process.

4)
Low power consumption of equipment -from 2 to 15 kW.
Thus, the developed SCF-extraction unit fully complies with the main criteria of environmental friendliness, efficiency, safety for processing plant raw materials in accordance with the standards for natural food ingredients in its mobile version. The presented installation expands this class of equipment and allows you to extract numerous types of plant raw materials and to compete with known analogues. In our arsenal there are the possibilities for the production of SCF equipment and optimization of the technological cycle for extracting various types of modes of SCF technology for the qualitative and quantitative composition of extracts.

Samples of Extracts
With the help of the declared equipment, we have obtained a number of fatty and aqueous solutions of bio-extracts. (Figures   1-3) shows that their chromatograms have 2-6 characteristic peaks corresponding to the yield of the basic components of the extract.
The most successful versions of ekstraction products are designed in the form of commercial series (Figure 4). 1. CO2 ballon-cylinder; 2. Refrigeration equipment; 3. Heat exchanger; 4. High-density compressor; 5. Heater; 6. Extractor; 7. Throttling valve; 8. Flow-changer in throttling valve when the high-density is dropped; 9. Shut-off valves; 10. Separator; 11. Container for receiving the extract; 12. Filter.  b) The proposed model of the CO 2 extraction plant has a number of advantages over the known analogs and creates competitive opportunities for prospective use as an alternative mobile equipment in world markets.