Separation of Substances from Highly Viscous Systems by High Pressure Extraction Processes

Separation or formulation of products by supercritical fluids and production of substances and composites with unique properties and characteristics for the use in different applications are nowadays intensively studied. One of the most important advantages using supercritical fluids is selective extraction of components or fractionation of total extracts. As yet, industrial dense gas extraction process units were used with maximum operating pressure up to 750 bar, but usual operating pressure was up to 500 bar. From literature it is known that the total yield increases with increasing pressure, due to higher solubility of substances in dense gases and, furthermore, for less soluble substances co-solvents (entrainers) could be used. Of late, in addition to previous installations, also a small scale plant designed for ultra high pressure (2.500 bar) extraction and selective multi-stage fractionation of substances from plant materials is in operation. Highly viscous systems were mostly processed using conventional solvents for viscosity reduction. The main disadvantage using conventional solvents is that the extracts are contaminated with organic solvents which can not be easily removed. The legal limitations of solvent residues and solvents (for products for use in human applications) and isolation/fractionation of special components from total extracts in combination with different formulation and sterilization processes will increase the use of dense gases for extraction applications. Examples on selective extraction of components from highly viscous systems like separation of lecithin from degumming residues and others will be presented. Also fundamental data on phase equilibrium for these systems as well as process and mechanical design of equipment and economy of the process will be dealt with.