Supercritical CO 2 extraction of ethanol from fermentation broth in a semicontinuous system

Abstract

Extraction of ethanol from fermentation broth was investigated under different operating conditions (313 K, 100–140 atm, 0.5–7.5 ml feed CO 2 min −1), in a system which is continuous in terms of CO 2, and batch in terms of fermentation broth. The experimental system consists of mainly four parts: the CO 2 storage system, the high pressure liquid pump, the extractor and the product collection unit. Samples were analysed by a gas chromatograph. The main objective of the extraction experiments was to explore the effects of CO 2 feed rate, extraction time and pressure on the extraction yield. Experiments that were carried out at 313 K, under 100 atm pressure and at seven different CO 2 feed rates demonstrated that the extraction yield is closely related to the CO 2 feed rate. While 13% of the initial ethanol load was extracted at 0.75 ml min −1 CO 2 feed rate after 5 h, 72% extraction was accomplished at 7.5 ml min −1 and at the same extraction time. It was also observed that extraction yield is a close function of extraction time. The effect of pressure on the extraction yield was investigated at 313 K under 100, 120 and 140 atm pressures. Although a pressure effect has not been established yet, there is some evidence that the increased pressures help to achieve higher yields.