Efficient Ethanol Recovery from Yeast Fermentation Broth with Integrated Distillation–Membrane Process

Abstract

A hybrid process integrating vapor stripping with vapor compression and vapor permeation membrane separation, termed Membrane Assisted Vapor Stripping (MAVS), was evaluated for recovery and dehydration of ethanol from aqueous solution as an alternative to conventional distillation–molecular sieve processes. Ethanol removal/drying performance of the MAVS system with binary ethanol–water mixtures and a yeast fermentation broth were evaluated and the fate of secondary fermentation products in the system was assessed. Simple alcohols, esters, and organic acids displayed varying degrees of recovery in the vapor stripping based on the relative vapor–liquid partitioning of the compounds. All volatilized organic compounds were concentrated to the same degree in the membrane step. Membrane permeance, permselectivity, and overall energy usage of the hybrid process were the same with the fermentation broth as with binary ethanol–water solutions. The MAVS system required less than half the energy of a distillation–molecular sieve system.