Characterization of the integrated gas stripping-condensation process for organic solvent removal from model acetone-butanol-ethanol aqueous solution

Abstract

During ABE fermentation, the bacterial toxicity of produced solvents, especially butanol at a high concentration, can cause low butanol productivity. This study aimed to characterize an integrated gas stripping and novel ABE recovery system using two-stage condensation equipped with an absorption unit for butanol recovery from the model ABE aqueous solution. The potential off-gas from ABE fermentation had 20–60% H2 balanced with CO2, along with low-cost inert N2 as stripping gas mix, at the volume of gas per volume of liquid per minute (vvm) set at 0.5, 1.0, and 1.5. The results showed that butanol was the most selective in the stripping, followed by acetone, ethanol, butyric, and acetic. The trend of stripping rate was opposite to the trend of condensation efficiency. Using 1.5 vvm nitrogen could achieve the highest stripping efficiency with butanol removal rate of 1.48 g/L·h, while the highest condensation efficiency of stripped ABE was obtained by using 20% H2 in gas mix at 0.5 vvm. The recovered butanol in condensate had high concentrations of 80–170 g/L. According to the results obtained, the integrated stripping process has potential to reduce butanol in fermentation broth and produce concentrated butanol in condensate that can be further purified at reduced energy cost.