Supercritical CO2 extraction at industrial scale: advantages of utilizing a number of extractors in series working in the counter-current mode

Different models are available in the literature to predict the course of an extraction with supercritical CO2 as solvent. In the general case, they focus on the fundamentals governing the extraction: mass transfer phenomena and, eventually, thermodynamics. This work presents a completely different approach: the same models are utilized to design industrial processes. The focus is on the advantages related to the utilization of a number of extractor in series (three to seven) working in the counter-current mode. The case study is represented by the supercritical CO2 extraction of grape seed oil, letting equal to 3000 ton/year the throughput of the plant (availability of the grape seeds according to figures of an Italian province: Trentino). Our results show the dependence of the extraction yield on the number of extractors: the adoption of four to six extractors in series seems preferable. The increase in extraction efficiency is sensible when increasing the number of extractors from 2 to 3 and from 3 to 4, while it becomes smaller when increasing further the number of extractors. In addition to this, the effect of plant and process variables is analysed: the extractor geometry (ratio diameter/height) and the solvent flow rate.