Extractive distillation to produce anhydrous bioethanol with choline chloride with urea (1:2) as a solvent : a comparative evaluation of the equilibrium and the rate-based models

ABSTRACT The purification of bioethanol to achieve anhydrous purity standards requires separation processes other than conventional distillation, such as extractive distillation. Different solvents have been studied to find alternatives to ethylene glycol, which is widely used in this application. In this study, the aim is to find the column configuration that offers the minimum total annual cost (TAC), considering a more realistic modeling than the equilibrium stage approach for the extractive distillation with ChCl:Urea (1:2) under atmospheric pressure. This evaluation uses the rate-based modeling in the Aspen Plus® simulator. The equilibrium stage model results show that, for the same number of distillation stages and solvent flow rate, ChCl:Urea (1:2) offers from 27 to 43 % lower energy requirement for the extractive distillation process than ethylene glycol. In addition, for the same number of distillation stages it is required lower solvent amount of ChCl:Urea (1:2) in comparison with ethylene glycol. Considering the configurations of each mole flow evaluated of ChCl:Urea (1:2), on average, the rate-based simulation required columns with 62 % more stages and 8.4 % higher TAC than the equilibrium simulation. These results demonstrate the importance of considering mass and heat transfer effects to model the real process.