Production of pure ethanol from azeotropic solution by pressure swing adsorption

Abstract

Pressure swing adsorption (PSA) is attractive for final separation in the process of water removal especially for fuel ethanol production. Despite many researches on simulation and experimental works on adsorption of water on 3A zeolite in a fixed bed, none have studied a process with the actual PSA system. The purpose of this research was to study the PSA process with two adsorbers and effects of several parameters. The research also included analysis of kinetic and thermodynamic data of ethanol-water adsorption on commercial 3A zeolites in a single fixed bed. A two-level factorial design experiment was used in this research work to preliminarily screen the influence and interaction among the factors. Effects of important parameters such as initial temperature, feed concentration and feed rate were investigated. It was proven that the Langmuir isotherm could best predict the experimental results. In the PSA pilot test, the principal factors, which had effects on the performance, were feed rate, feed concentration, adsorption pressure and the cycle time. Prediction of the process efficiency in terms of ethanol recovery and enrichment was proposed in the form of regression models. The results of the study in a fixed bed adsorber could help designing a pilot-scale PSA unit. The experiments proved to be successful in terms of producing high concentration ethanol with high percentage of ethanol recovery. With further simulation work the process could be scaled up for an industrial use.