Supercritical CO2 oilseed extraction in multi-vessel plants. 2. Effect of number and geometry of extractors on production cost |
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| Affiliation: | 1. Department of Chemical and Environmental Engineering, Universidad Técnica Federico Santa María, Av. Vicuña Mackenna 3939, San Joaquín, Santiago, Chile;2. Department of Chemical and Bioprocess Engineering, Pontificia Universidad Católica de Chile, Avda. Vicuña Mackenna 4860, Macul, Santiago, Chile;3. ASIS-UC Interdisciplinary Research Program on Tasty and Healthy Foods, UC, Santiago, Chile;1. School of Chemical and Petroleum Engineering, Shiraz University, Mollasadra Ave., Shiraz 71345, Iran;2. Delft University of Technology, Faculty of Science and Technology, Department of Chemical Technology, Julianalaan 136, 2628 BL Delft, The Netherlands;3. The Petroleum Institute, Chemical Engineering Department, P.O. Box 2533, Abu Dhabi, United Arab Emirates;4. Eindhoven University of Technology, Department of Chemical Engineering and Chemistry, Separation Technology Group, Den Dolech 2, 5612 AZ Eindhoven, The Netherlands;1. Institute of Chemical and Environmental Technology, Department of Chemical Engineering, University of Castilla-la Mancha, Campus Universitario, s/n, 13071, Ciudad Real, Spain;2. School of Chemistry, University Park, Nottingham NG7 2RD, UK;1. High Pressure Processes Group, Chemical Engineering and Environmental Technology, University of Valladolid, Doctor Mergelina s/n, 47011 Valladolid, Spain;2. Department of Industrial Chemistry and Polymers, School of Industrial Engineering, Polytechnic University of Madrid, Spain;3. Departamento de Física, Instituto de Física Aplicada, Universidad Nacional de San Luis-CONICET, Chacabuco 917, D5700BWS San Luis, Argentina;4. Facultad de Ciencias Químicas, Universidad Nacional de Córdoba – CONICET, Haya de la Torre y Medina Allende, Ciudad Universitaria, X5000HUA Córdoba, Argentina |
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| Abstract: | The objective of this work was to study production costs for the supercritical CO2 extraction of a pre-pressed oilseed (packed bed with 2-mm particles) in a 2-m3 industrial multi-vessel plant operating at 40 °C and 30 MPa, using a fully predictive mass transfer model to simulate the process. We modified the inner diameter (47.3 ≤ D ≤ 65.6 cm) and number (n = 2, 3, or 4) of extraction vessels, and the mass flow rate of CO2 (Q = 3000 or 6000 kg/h), thus changing the aspect ratio of the extraction vessels (3 ≤ L/D ≤ 8), and superficial velocity (2.71 ≤ U ≤ 10.8 mm/s) and specific mass flow rate (6 ≤ q ≤ 24 kg/h per kg substrate) of CO2. Production cost decreased when increasing the mass flow rate of CO2 or the number of extraction vessels (or when increasing q). Production cost did not depend on the geometry of extraction vessel for a constant specific mass flow rate of CO2, but it decreased with a decreasing of the L/D ratio of the vessel for a constant superficial velocity of CO2. For any given plant, the contribution of fixed cost items (capital, labor) to the production cost increased with extraction time, unlike that of variable cost items (substrate, CO2, energy), which decreased. Thus, there was an optimal extraction time that minimized production cost for each plant. This work proposes an expression for capital cost of an industrial multi-vessel plant as a function of the mass flow rate of CO2 (which defines the cost of the solvent cycle of the plant), and the volume of the extraction vessels (which together with number of extraction vessels define the cost of extraction section of the plant), with a scaling factor of 0.48 for both items. Under optimal conditions, capital cost represented 30–40% of the production cost, but uncertainties in capital cost estimates (about ±50% using the proposed expression) may largely affect these estimates. The lowest production cost estimated in this work was USD 7.8/kg oil for the extraction of prepressed oilseed in a four-vessel plant using 6000 kg/h of CO2. The mass flow rate of CO2 and number of extraction vessels also affected annual productivity that was about 360 ton oil for the same plant operating 7200 h per year. Oil yields were above 90% for both three- and four-vessel plants. |
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| Keywords: | Capital cost Industrial plant Optimal extraction time Prepressed oilseed Production cost Residence time |
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