Regresar

Effect of high power ultrasounds on mass-transfer zone in supercritical fluid extraction processes

Abstract:

Supercritical fluid extraction (SFE) is a recent technology that is based on the solvent power that some fluids exhibit under pressure and temperature above certain values named as critical point. This process, using supercritical CO 2 as solvent, has gained wide acceptance in the last decades, because of its advantages compared to conventional solvent extraction ones (high selectivity, non toxic, inert, suitable to extract thermolabile substances, cheap, recyclable). One of the main difficulties of SFE is to achieve favourable kinetics due to the fact that mechanical stirring is not easyly applied to an extractor vessel operating at high pressures. In this context, an interesting alternative is the use of power ultrasound. Ultrasonic radiation represents an efficient way to enhance mass transfer processes, because of some mechanisms such as microstirring, compressions and decompressions in the material, heating, and/or cavitation. Previous works of this research group pointed out the feasibility of integrating an ultrasonic field inside a supercritical extractor without losing a significant volume fraction. Moreover, a new self-controlled prototype, robust enough to fulfill industrial requirements to produce it commercially was developed and tested under supercritical conditions, giving rise to a non-antecedent patent. This new ultrasonic device led to notable enhancement both on extraction yields at certain times and on required time to achieve a certain extraction yield when applied on SFE almond oil. Some experiments carried out gave rise to yields 20% greater than those without ultrasounds. In order to deepen in the knowledge of this new technology, the aim of this work was to study the effect of High Power Ultrasounds (HPU) on mass transfer zone (MTZ) in the supercritical extraction. For this purpose, different tests have been performed to assess the effect of HPU on SFE of oil from milled almonds (3-4 mm particle size). To examine the effect of the acoustic waves all experiments were performed with and without ultrasound at identical pressure, temperature and flowrate conditions. In this work, the effect of high-intensity ultrasonic waves on mass-transfer zone based on oil concentration profiles at different times and bed heights are discussed. Copyright © (2010) by the International Congress on Acoustics.