(331b) Membrane Assisted Vapor Stripping: Reduced Cost and Energy Usage for Alcohol-Water Separation

Alcohols, including ethanol and butanols, are receiving increased attention as renewable liquid biofuels.  Fermentative production of alcohols, particularly butanols like 1-butanol and isobutanol, is limited to low concentrations due to product inhibition and limited lignocellulosic-based substrate concentrations. The result is high separation energy demand by conventional distillation approaches, despite favorable vapor-liquid equilibrium and, for butanol, partial miscibility with water.  In previous work from our group, a process integrating steam stripping, vapor compression, and vapor permeation separation was proposed and evaluated for separating ethanol, 1-butanol, and acetone/butanol/ethanol (ABE) mixtures from water.  Such a Membrane Assisted Vapor Stripping (MAVS) process was found to be 60-70% more energy efficient than conventional distillation approaches.  In such hybrid distillation/membrane MAVS systems, the stripping column provides high alcohol recovery and low effluent concentration while the vapor compression and membrane steps enable the efficient recovery of latent and sensible heat from both the retentate and permeate streams from the membrane system.  In this work, capital costs and energy usage for simulated 2^nd generation MAVS designs will be discussed.