Extraction of natural compounds using supercritical CO2: Going from the laboratory to the industrial application

• Published in: The Journal of supercritical fluids 2015-01, Vol.96, p.180-199
• Main Author: del Valle, José M.
• Format: Article
• Language: English
• Subjects: Extraction; Industrial plant; Optimal extraction time; Prepressed oilseed; Process design; Production cost; Supercritical CO2; Vegetable oil
• ISSN: 0896-8446; 1872-8162
• DOI: 10.1016/j.supflu.2014.10.001

•Experiments provide a mass transfer parameter for optimally pretreated substrates.•Computer simulation (CS) helps optimizing industrial multi-vessel (MV) SFE plants.•Pilot plant data will help refining simulation code to account for nonideal flow conditions.•CS may be the single tool permitting the multivariable optimization required for MV SFEs.•Technical restrictions to particle size, CO2 velocity, and plant cycle time await identification. Despite industrial application for almost four decades, there is reluctance in some world regions to adopt supercritical (sc) CO2 extraction because of the wrong perception that it is not fully competitive. To refute this misconception, this manuscript analyzes economics of scCO2 extraction of vegetable oil from prepressed seeds. Selection of this application was due to the availability of a predictive mathematical model of the extraction process applicable for simulation purposes; inner microstructural changes of oilseeds during prepressing allow their extraction according to a shrinking core hypothesis. The predictive model has as its single parameter a particle-size and scCO2-condition-independent microstructural mass transfer factor that can be best-fitted to laboratory extractions, existing literature correlations to estimate other model parameters, such as the axial dispersion in packed beds operating with supercritical fluids, and the solubility of vegetable oils in scCO2. On the other hand, there is a need to correlate literature data for the film mass transfer coefficient to unveil the factors responsible for experimental data scattering. Because laboratory or pilot plant runs in single-extraction-vessel units cannot produce the simulated countercurrent contact in an industrial plant having ≥3 extraction vessels, mathematical simulation provides the relationship between oil yield and extraction time that can anchor precise estimations of extraction cost. Analysis of results unveiled differences in optimal extraction time (for minimal extraction cost) between production costs estimated in this work and the operational costs informed before. Because the operational cost does not include the capital cost of the industrial plant, the need appears to reduce its contribution to the total cost by increasing plant productivity. This is achieved reducing extraction time, which negatively influences oil yield. To make further progress in the optimization of industrial scCO2 extraction processes, this manuscript propos