Avaliação de novas configurações da destilação extrativa para obtenção de etanol anidro.

Abstract

Extractive distillation is commonly used for the separation of chemical mixtures that form azeotropes or have low relative volatilities. Unfortunately, extractive distillation is considered to be a major energy user. The separation of system ethanol-water is the main problem in the production of the alcohol for fermentation; because the feeding is diluited,needing great amount of energy for its recovery, until close of its azeotrope composition , for conventional distillation.The object of the present work to decrease the energy consumption. The conventional three-column extractive distillation system for ethanol water separation with ethylene glycol as the solvent. The first column concentrates the ethanol in the dilute feed and produces a pure water bottoms product. The second column adds solvent to make the azeotrope disappear allowing production of a pure ethanol distillate. The third column recovers solvent for recycle and produces a water distillate. New flow sheets to reduce the energy use in extractive distillation to break azeotropes were developed and discussed in this article. One defining feature of the standard process is that steam product is taken from the total condenser of column 1 to be fed into column 2 . There is an optimum concentration of the distillate product from column 1 in both flow sheets. Approaching the azeotropic concentration in column 1 increases the energy input and the capital investment in column 1, but reduces the energy and equipment costs required for columns 2 and 3. Another interesting extractive distillation process combines columns 2 and 3. This requires recycle of the distillate from column 3 to column 1. To operate properly, the process in must have Pcoiumn3 > Pcoiumni > Pcoiumn2- This can be done conveniently by using a pump on the bottoms from column 2.