Energy optimization of supercritical fluid extraction processes with separation at supercritical pressure

Production costs for supercritical fluid extraction of natural substances are significantly influenced by the energy requirement. Energy costs are calculated for a large number of process variants of four different types of process with separation at supercritical pressure. The process parameter ranges investigated are: extraction pressure, 30–50 MPa; extraction temperature, 40–100°C; separation pressure, 8–49.75 MPa. The extraction of oil from soybeans is taken as an example. The results, presented in tables and diagrams, also apply to the extraction of other oils whose solubility in CO2 resembles that of soybean oil. Extraction at 50 MPa and 100°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 should not exceed 15 MPa. The calculated energy costs, together with data for the kg soybean oil produced per kg CO2, form the basis for designing an economically optimized supercritical fluid extraction plant.