Improved Energy Efficiency of a Hybrid Pervaporation/Distillation Process for Acetic Acid Production: Identification of Target Membrane Performances by Simulation

The continuously rising cost of world energy is pushing the chemical process industry to find alternative processes to conventional separation processes. Previous studies on hybrid processes coupling pervaporation or vapor permeation with distillation have claimed interesting decreases in energy consumption compared to conventional processes. However, most of the time, it remains difficult to really evaluate the actual potential and the energy gain achievable for a membrane process for a particular separation. This paper reports an innovative simulation methodology that can be applied to determine the membrane performances that have to be achieved to replace conventional processes with a hybrid process while respecting constraints that are fixed by industrial specifications. This method is applied to the case of acetic acid dehydration. A hybrid process consisting of a pervaporation module equipped with a hydrophilic membrane coupled with a distillation column is proposed and studied. The minimum membrane performances for industrial use of pervaporation are determined and compared to membrane performances that have already been reported in the literature. As a result, this work shows that commercially available membranes have a selectivity that is too low to induce significant economic savings for this application, although some materials that are not yet commercialized show very interesting separation results.