Extraction Technologies for Medicinal and Aromatic ... - Capacity4Dev
Extraction Technologies for Medicinal and Aromatic ... - Capacity4Dev Extraction Technologies for Medicinal and Aromatic ... - Capacity4Dev
10 SUPERCRITICAL FLUID EXTRACTION OF MEDICINAL AND AROMATIC PLANTS: FUNDAMENTALS AND APPLICATIONS To measure extraction profiles, a small pilot-scale apparatus can be used. Extractor and separator volumes do not need to exceed 1 liter each. The analytical system must be suitable to measure the concentration and purity of the products of interest. Basic requirements in terms of equipment are: 1. A liquid CO2 storage tank 2. A pump for liquid CO2 3. A cooler to prevent CO2 from evaporating in the pump 4. A heat exchanger to control the temperature of CO2 entering the extractor 5. An extraction vessel 6. A heat exchanger to control the CO2 plus solute mixture entering the separator 7. A separation vessel Note that condensing and recycling of CO 2 after separation is not needed at the laboratory-scale developmental level, whereas these are essential requirements at the industrial production level. All parts of the SFE laboratory-scale plant must be designed in order to resist the maximum operating pressure. If this does not exceed 300-350 bar, the entire equipment (e.g. vessels, valves, fi ttings) is pretty much of standard type and relatively inexpensive. If, as usual, stainless steel is used, the thickness of any part of the plant can be easily calculated by applying the Von-Mises equation: k P 2 i k 2 – 1 √⎯3 < σ am (5) with: σ am = σ s (6) S f where P i is the internal pressure, k is the external to internal diameter ratio, σ s is the yield stress, and S f is a suitable safety factor (usually S f =1.5). From Eq. 5, it can be seen that the thickness of a cylindrical vessel depends on its diameter. Examples are given in Table 1 for a vessel of 0.2 m internal diameter, with both stainless steel and carbon steel construction materials. Table 1: Thickness (s) of a thick-wall cylindrical vessel of 200 mm internal diameter as a function of pressure (SS=stainless steel, CS=carbon steel) P [atm] 50 100 150 200 250 300 s [mm] SS 3.8 8.1 12.9 18.5 25.0 32.7 CS 2.2 4.6 7.2 10.0 13.0 16.2 176
EXTRACTION TECHNOLOGIES FOR MEDICINAL AND AROMATIC PLANTS Special care must be paid to closures and seals. SFE of MAPs is mostly an extraction operation from solid materials, which is carried out in batch or semibatch mode. Therefore, extraction vessels need to be pressurized, depressurized, opened, fi lled, and closed again several times per day. In order to ensure fast and safe operation procedures and reliable seals, gaskets like O-rings are useful and closure devices have been specifi cally designed. Again, the technology needed is already fully developed. We refer to chapter 4 of the book by Bertucco and Vetter for details. The book also describes the machinery for moving fl uids under pressure, i.e. pumps and compressors. We conclude that setting up a laboratory-scale apparatus with which to perform feasibility studies concerning the possibility of applying SFE to MAPs is not really an issue, and can be done with a relatively small capital cost. However, this does not mean that SFE of MAPs is in itself an economically convenient operation. An accurate evaluation of production costs, including both capital and utility costs, must be performed before scaling up a process whose technical feasibility has been demonstrated at the laboratory level. Costs are also discussed in the book by Bertucco and Vetter (chapter 8), but are only indicative. The reader should remember that capital costs have been steadily decreasing in the last years must be taken into account. 10.5 SFE Applied to Medicinal and Aromatic Plants A large number of MAPs has been considered for possible extraction by supercritical CO 2 . The most recent developments suitable to have industrial relevance are listed in Table 2. These examples illustrate the great potential of SFE in this fi eld. Table 2: Medicinal and aromatic plants extracted by SFE Plant name (part used) Calendula offi cinalis (fl owers) Product(s) extracted Oleoresin Reference Campos et al., 2005, Experimental data and modeling the supercritical fl uid extraction of marigold (Calendula offi cinalis) oleoresin, J Supercritical Fluids, 34: 163-170 Danielski et al., 2007, Marigold (Calendula offi cinalis L.) oleoresin: solubility in SC-CO 2 and composition profi le, Chem Eng Proc, 46: 99–106 177
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EXTRACTION TECHNOLOGIES FOR MEDICINAL AND AROMATIC PLANTS<br />
Special care must be paid to closures <strong>and</strong> seals. SFE of MAPs<br />
is mostly an extraction operation from solid materials, which is carried out in<br />
batch or semibatch mode. There<strong>for</strong>e, extraction vessels need to be pressurized,<br />
depressurized, opened, fi lled, <strong>and</strong> closed again several times per day.<br />
In order to ensure fast <strong>and</strong> safe operation procedures <strong>and</strong> reliable seals,<br />
gaskets like O-rings are useful <strong>and</strong> closure devices have been specifi cally<br />
designed. Again, the technology needed is already fully developed. We refer<br />
to chapter 4 of the book by Bertucco <strong>and</strong> Vetter <strong>for</strong> details. The book also<br />
describes the machinery <strong>for</strong> moving fl uids under pressure, i.e. pumps <strong>and</strong><br />
compressors. We conclude that setting up a laboratory-scale apparatus with<br />
which to per<strong>for</strong>m feasibility studies concerning the possibility of applying<br />
SFE to MAPs is not really an issue, <strong>and</strong> can be done with a relatively small<br />
capital cost.<br />
However, this does not mean that SFE of MAPs is in itself an<br />
economically convenient operation. An accurate evaluation of production<br />
costs, including both capital <strong>and</strong> utility costs, must be per<strong>for</strong>med be<strong>for</strong>e<br />
scaling up a process whose technical feasibility has been demonstrated at<br />
the laboratory level. Costs are also discussed in the book by Bertucco <strong>and</strong><br />
Vetter (chapter 8), but are only indicative. The reader should remember that<br />
capital costs have been steadily decreasing in the last years must be taken<br />
into account.<br />
10.5 SFE Applied to <strong>Medicinal</strong> <strong>and</strong> <strong>Aromatic</strong><br />
Plants<br />
A large number of MAPs has been considered <strong>for</strong> possible<br />
extraction by supercritical CO 2 . The most recent developments suitable to<br />
have industrial relevance are listed in Table 2. These examples illustrate the<br />
great potential of SFE in this fi eld.<br />
Table 2: <strong>Medicinal</strong> <strong>and</strong> aromatic plants extracted by SFE<br />
Plant name<br />
(part used)<br />
Calendula<br />
offi cinalis<br />
(fl owers)<br />
Product(s) extracted<br />
Oleoresin<br />
Reference<br />
Campos et al., 2005, Experimental<br />
data <strong>and</strong> modeling the supercritical<br />
fl uid extraction of marigold (Calendula<br />
offi cinalis) oleoresin, J Supercritical<br />
Fluids, 34: 163-170<br />
Danielski et al., 2007, Marigold<br />
(Calendula offi cinalis L.) oleoresin:<br />
solubility in SC-CO 2 <strong>and</strong> composition<br />
profi le, Chem Eng Proc, 46: 99–106<br />
177