Swelling of plant material under the influence of supercritical carbon dioxide – mathematical modelling and optimization of the process of supercritical fluid extraction

Abstract

The subject of this disertation is the swelling of plant material under the influence of supercritical carbon dioxide, as well as the effects of swelling on the process of supercritical fluid extraction (SFE). The results of experiments on the kinetics of the SFE processes were modeled using a mathematical model on the micro-scale and the Sovova’s model, which quantitatively express, through the parameters of the model, the changes that occur due to the swelling of plant material. The swelling of glandular trichomes of plants of the Lamiaceae family, swelling of hop in the form of ground particles of plant material and industrial granulates, and swelling of the particles of valerian root and rhizome of ginger were observed. The tests were conducted in order to examine the possibility of optimization the SFE process in respect to the consumption of supercritical fluids and energy. For the process of SFE of essential oils from glandular trichomes, a complex mathematical model which includes the cracking time distribution for glandular trichomes was developed. The new model describes the process of SFE with significantly higher accuracy than the existing mathematical models. For extraction at higher pressures the optimal pretreatment of plant material is defined with the goal to achieve significant savings of supercritical fluid. In the case of swelling of hops, the mass transport phenomena in granulates and cones exposed to supercritical fluid in various conditions were considered. The results explained phenomena that occur on industrial scale, especially undesirable hardening of the extraction cake. Process parameters (diffusion coefficients in the solid phase) are described by applying mathematical models to experimental results. In the case of swelling of valerian root and rhizome of ginger, significant savings of supercritical fluid consumption were achieved by choosing the optimal treatment. Process parameters (coefficients of mass transfer through the solid phase) are described by applying mathematical models to experimental results.

Tema ove doktorske disertacije je ispitivanje bubrenja biljnog materijala pod uticajem natkritičnog ugljenik(IV)-oksida, kao i efekata koje bubrenje ima na proces natkritične ekstrakcije (NKE). Na rezultate eksperimenata u kojima je praćena kinetika procesa NKE primenjen je matematički model na nivou sekrecione strukture i model Sovove, kako bi se promene do kojih dolazi usled bubrenja biljnog materijala kvantitativno izrazile preko parametara modela. Ispitano je bubrenje glandularnih trihoma biljaka familije Lamiaceae, bubrenje hmelja u vidu mlevenih čestica biljnog materijala i industrijskih granulata, i bubrenje čestica korena odoljena i rizoma đumbira. Ispitivanja su vođena u pravcu optimizacije procesa NKE u odnosu na potrošnju natkritičnog fluida i energije. Za proces NKE etarskih ulja iz glandularnih trihoma razvijen je kompleksan matematički model koji uključuje raspodelu vremena pucanja glandularnih trihoma, koji opisuje proces NKE sa znatno većom tačnošću u odnosu na postojeće matematičke modele. Za ekstrakciju na višim pritiscima definisan je optimalan predtretman biljnog materijala kojim se postižu značajne uštede natkritičnog fluida. U slučaju bubrenja hmelja razmatrani su fenomeni prenosa mase u šišaricama i granulatima hmelja izloženim natkritičnom fluidu na različitim uslovima. Rezultati su objasnili pojave koje se dešavaju na industrijskom nivou, a pre svega nepoželjno očvršćavanje ekstrakcione pogače. Parametri procesa (koeficijenti difuzije kroz čvrstu fazu) opisani su primenom matematičkih modela na eksperimentalne rezultate. U slučaju bubrenja korena odoljena i rizoma đumbira, izborom optimalnog predtretmana ostvarene su značajne uštede natkritičnog fluida. Parametri procesa (koeficijenti prenosa mase kroz čvrstu fazu) opisani su primenom matematičkih modela na eksperimentaln rezultate.