Design and control of an alternative distillation sequence for bioethanol purification

BACKGROUND: Bioethanol is a green fuel considered to be a sustainable alternative to petro-derived gasoline. The transport sector contributes significantly to carbon dioxide emission and consequently has a negative impact on the air quality and is responsible for the increase of the greenhouse effect. The availability of environment-friendly and economical fuels is a worldwide priority. The separation process is a significant technology in the production of fuel grade ethanol in terms of both operating and capital costs. In the present work an alternative distillation sequence for bioethanol separation is presented. The steady state performance and the dynamic beavior are analyzed compared with the classical configuration reported in the literature. RESULTS: Ethanol-water azeotropic separation represents a challenge for bioethanol purification. Usually a three column sequence is used to obtain fuel grade bioethanol by extractive distillation. In order to reduce bioethanol purification cost a two column separation sequence is proposed. This configuration shows a 10% saving in capital costs together with higher ethanol recovery and better control properties compared with the classical three column sequence. CONCLUSIONS: Based on the steady state and dynamic results obtained, the two-column configuration represents a valid alternative to the classical configuration for the separation of bioethanol.