Recovery of Near-Anhydrous Ethanol as Gasoline Additive from Fermentation Products

Abstract

The use of near-anhydrous ethanol, obtained from fermentation products through low pressure distillation, as a gasoline additive is examined. To this purpose, a reliable model for predicting the azeotropic composition of an ethanol-water mixture as a function of the pressure is presented. It is developed by considering the available thermodynamic consistent experimental data and using the Wilson and the Virial equations for the liquid- and vapor-phase nonideality, respectively. It is concluded that, for an area with no extremely cold winters—minimum ambient temperature ?20°C—alcohol with 96.5% (wt) purity can be used in a 90/10 (vol) gasohol mixture. Such an alcohol can be produced with a single distillation column operating at 140 mmHg pressure with an energy consumption of 5150 kJ/kg of product; or with a system of two columns with lower energy consumption but higher capital cost. These energy consumptions are very sensitive to the accuracy of the predicted azeotropic composition at the operating pressures.