A combined gas-stripping vapour permeation process for aroma recovery

A new aroma recovery process was proposed, in which aroma extraction is brought about by gas stripping in a bubble column and aroma concentration is performed by vapour permeation. After the construction and proper characterisation of a polydimethylsiloxane (PDMS) hollow-fibre module, experimental runs were conducted with air and diluted ethyl acetate aqueous solutions in order to illustrate the adequacy of the proposed process. In these tests, a multi-stage condensation system comprising four traps placed in series was employed for collecting the permeate. Even though rather diluted feed streams were used, recovery degrees as high as 98% were observed. Three gas flow rates were investigated and the effect of this parameter on the process performance was systematically analysed. In addition, aroma pervaporation tests were also conducted with the constructed PDMS module and a comparison between the results obtained with the two membrane processes was made. This comparison provided an experimental verification of the equality of mass flux calculation in vapour permeation and pervaporation when it is based on the chemical species fugacity difference across the membrane.