Modelling and optimization of energy consumption in essential oil extraction processes

The aim of this study is the modelling and the optimization of energy consumption during essential oils extraction by conventional and microwave assisted processes. As regards energy efficiency assessment, an indicator has been developed and used that reflects the evolution of energy consumed per mass unit of essential oil extracted. The adopted modelling approach allows, in addition of energy consumption estimation, to follow its evolution throughout the extraction process. For models validation purposes, a set of 170 extraction kinetics data reported in the literature was used. The results showed that the simulated energy consumption during the extraction process is in good agreement with the measured values in all studied cases. Also these results show that an increase of essential oil recovery rate from 90% to 99% induced an energy consumption multiplied by a factor between 1.8 and 11 whether in conventional processes or those assisted by microwaves. This increase of energy consumption per mass of extracted essential oil highlights the fact that targetting a maximal oil recovery through plant depletion, is neither an economical nor an ecological optimum. The comparison between classical and microwaves assisted processes showed that generally the use of microwave heating reduce energy consumption with a reduction factor varying between 2 and 10 regardless of the extraction yield. This modeling approach provides a valuable insight on the optimal work conditions in favor of a cleaner production of essential oils and can be considered as a precious tool for increasing efficiency in the use of energy and cost reduction. (C) 2019 Institution of Chemical Engineers. Published by Elsevier B.V. All rights reserved.