Steady State of an Extractive Distillation Column
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Consider an extractive distillation column operating at atmospheric pressure. This column has 22 stages, a partial reboiler, and a total condenser. It is used to obtain anhydrous ethanol using ethylene glycol as an entrainer.[more]
Pure entrainer at is fed to the column at a flow rate equal to and at stage two (counting from the top). The lower feed is composed of a mixture of ethanol and water ( ethanol and water). The lower feed, a saturated liquid, is located at stage 12 (counting from the top) and has a flow rate equal to .
The Demonstration solves the MESH equations (mass, equilibrium, summation, and heat) and displays the composition and temperature profiles for user-set values of the reflux ratio. The second degree of freedom is set by taking a distillate flow rate equal to .
Finally, a comparison of the present calculation with Aspen-HYSYS shows excellent agreement.[less]
Contributed by: Housam Binous and Naim Faqir (July 2012)
Open content licensed under CC BY-NC-SA
The expressions for pure component vapor and liquid enthalpies were adapted from Aspen HYSYS®.
The mixture is assumed to obey the modified Raoult's law, and the activity coefficients are predicted using the Wilson model.
 M. F. Doherty and M. F. Malone, Conceptual Design of Distillation Systems, Boston: McGraw–Hill, 2001.
 E. J. Henley and J. D. Seader, Equilibrium-Stage Separation Operations in Chemical Engineering, New York: Wiley, 1981.