Hybrid vapor stripping–vapor permeation process for recovery and dehydration of 1‐butanol and acetone/butanol/ethanol from dilute aqueous solutions. Part 2. Experimental validation with simple mixtures and actual fermentation broth

Abstract

AbstractBACKGROUNDIn Part1 of this work, a process integrating vapor stripping, vapor compression, and a vapor permeation membrane separation step, ‘membrane assisted vapor stripping’ (MAVS), was predicted to produce energy savings compared with traditional distillation systems for separating 1‐butanol/water and acetone‐butanol‐ethanol/water (ABE/water) mixtures. Here, the separation performance and energy usage of a MAVS pilot system with such mixtures and an ABE fermentation broth were assessed.ResultsThe simple stripping process required 10.4 MJ‐fuel kg–1‐butanol to achieve 85% butanol recovery from a 1.3 wt% solution. Addition of the vapor compressor and membrane unit and return of the membrane permeate to the column raised 1‐butanol content from 25 wt% in the stripping vapor to 95 wt% while cutting energy usage by 25%. Recovery of secondary fermentation products from the ABE broth were based on their relative vapor–liquid partitioning. All volatilized organic compounds were concentrated to roughly the same degree in the membrane step. Membrane permeance, selectivity, and overall MAVS energy usage were the same with the broth as with the ABE/water solution.ConclusionEnergy usage of the MAVS experimental unit corroborated process simulation predictions. Simulations of more advanced MAVS designs predict 74% energy savings compared with a distillation–decanter system. Published 2013. This article is a U.S. Government work and is in the public domain in the USA