Flash Distillation Cascade for an Ethyl Acetate-Ethanol Mixture

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A binary mixture, composed of ethyl acetate and ethanol, is fed to a flash distillation cascade. The mixture presents a positive azeotrope with 0.54 mole fraction ethyl acetate at a boiling point of 72.4°C. Vapor-liquid equilibrium data for the simulations are generated using a modified Raoult's law with activity coefficients predicted by the van Laar model. The user specifies the feed mixture composition as mole % ethyl acetate (labeled EA in the data tables).

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This Demonstration presents the flash distillation cascade leading to a vapor stream, with composition approaching the azeotropic composition when the number of flash operations is large enough, and an ethanol-rich or EA-rich liquid stream (depending on the user-set feed composition). The compositions of these two streams are given in blue and red, respectively.

Temperature is decreased in the rectifying cascade in order to produce the top vapor stream and increased in the stripping cascade so that an ethyl acetate-lean or an ethanol-lean liquid stream is obtained. The gradual temperature changes are adjusted so that the vapor fraction is always equal to 50% at the entrance of any flash vessel.

The simulations show in particular that pure ethanol and pure ethyl acetate cannot be obtained simultaneously even if you use a very large number of flash distillation vessels.

The VLE diagram selection shows the temperature changes as red and blue arrows as well as the location of the vapor streams in the rectifying cascade (shown as cyan dots). Finally, the liquid streams in the stripping cascade are shown using magenta dots.

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Contributed by: Housam Binous and Ahmed Bellagi (March 2011)
Open content licensed under CC BY-NC-SA


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