ENERGY OPTIMIZATION OF SUPERCRITICAL-FLUID EXTRACTION PROCESSES WITH SEPARATION AT SUPERCRITICAL PRESSURE

Production costs for supercritical fluid extraction of natural substan ces are significantly influenced by the energy requirement. Energy cos ts are calculated for a large number of process variants of four diffe rent types of process with separation at supercritical pressure. The p rocess parameter ranges investigated are: extraction pressure, 30-50 M Pa; extraction temperature, 40-100 degrees C; separation pressure, 8-4 9.75 MPa. The extraction of oil from soybeans is taken as an example. The results, presented in tables and diagrams, also apply to the extra ction of other oils whose solubility in CO, resembles that of soybean oil. Extraction at 50 MPa and 100 degrees C is recommended from energy considerations, but a lower extraction temperature may be required to preserve the quality of the extracted oil. The heat exchanger between extractor and separator can be omitted. The separation pressure shoul d not exceed 15 MPa. The calculated energy costs, together with data f or the kg soybean oil produced per kg CO,, form the basis for designin g an economically optimized supercritical fluid extraction plant. (C) 1998 Elsevier Science S.A. All rights reserved.