Hybrid vapor stripping–vapor permeation process for recovery and dehydration of 1‐butanol and acetone/butanol/ethanol from dilute aqueous solutions. Part 1. Process Simulations

Abstract

BACKGROUND: Fermentative production of butanol is limited to low concentrations, typically less than 2 wt% solvent, due to product inhibition. The result is high separation energy demand by conventional distillation approaches, despite favorable vapor-liquid equilibrium and partial miscibility with water. In previous work, a process integrating steam stripping, vapor compression, and vapor permeation separation was proposed for separating ethanol from water. Such a membrane assisted vapor stripping (MAVS) process is considered in this work for 1-butanol/water and acetone/butanol/ethanol/water (ABE/water) separation.RESULTS: Using process simulations, the earlier MAVS design was estimated to require 6.2 MJ-fuel kg −1 -butanol to produce 99.5 wt% 1-butanol from a 1 wt% 1-butanol feed, representing an energy savings of 63% relative to a benchmark distillation/decanter system. Adding a fractional condensation step to the original MAVS design is predicted to reduce energy demand to only 4.8 MJ-fuel kg −1 -butanol and reduce membrane area by 65%. CONCLUSION: In the hybrid distillation/membrane MAVS systems, the stripping column provides high butanol recovery and low effluent concentration while the vapor compression and membrane steps enable the efficient recovery of latent and sensibleheat from both the retentate and permeate streams from the membrane system. Addition of the dephlegmator condenser reduces both compressor size and membrane area. . c 2-phase azeotrope: upper phase = 30.8 wt% water, lower phase = 92.1 wt% water 34 d 2-phase azeotrope: upper phase = 15.0 wt% water, lower phase = 91.3 wt% water 50

Effect of membrane and process characteristics on cost and energy usage for separating alcohol-water mixtures using a hybrid vapor stripping-vapor permeation process

“…Similarly, 1 MJ of delivered steam heat corresponded to 1.11 MJ of fuel‐equivalents due to an assumed 90% boiler efficiency. As in our previous work, we employed the UNIQUAC thermodynamic model with 1‐butanol/water parameters from Fischer and Gmehling and values from the DECHEMA Chemistry Data Series for the ethanol/water and acetone/water pairs …”

“…The baseline membrane has a water/1‐butanol molar permselectivity of 1000 and a water permeance of 7774 GPU (2.6 × 10 −6 kmol/m 2 ·s·kPa). These values were chosen to match the permeances used in our previous simulation papers on this subject to present a consistent set of baseline simulations . They represent the general properties of a 2 µm thick poly(allyl amine‐hydrochloride)‐poly(vinyl alcohol) blend selective layer developed in our laboratory with water and alcohol permeabilities of 5.2 × 10 −12 and 5.2 × 10 −15 kmol · m/m 2 · s · kPa, respectively .…”

“…The subject of this paper is one such synergistic hybrid, termed Membrane Assisted Vapor Stripping (MAVS), combining distillation‐based vapor stripping and membrane‐based vapor permeation in a manner that significantly reduces energy usage for the recovery of volatile solvents and biofuels from water . A schematic diagram of a ‘2nd generation’ MAVS process is shown in Fig.…”

“…In our previous publications on the subject, we have described the general theory behind MAVS processes, simulation predictions for performance and initial cost estimates, energy demand, and experimental verifications for ethanol/water, 1‐butanol/water, and acetone/1‐butanol/ethanol/water (ABE/water) systems . In this paper, we evaluate the effect of a variety of process variables and membrane performance/unit cost characteristics on energy usage and the overall separation cost for MAVS systems.…”

Simultaneous VLLE data correlation for ternary systems: Modification of the NRTL equation for improved calculations

“…For instance, in the fuel and biofuel industry or chemicals and polymers production, these kinds of water + alcohol + solvent mixtures with a VLLE behaviour have to be purified by using different techniques, such as azeotropic distillation, liquidliquid extraction, extractive distillation, adsorption, pervaporation, etc. [13][14][15][16].…”