Consider a non-ideal binary mixture composed of ethanol/ethyl acetate. This mixture presents a positive azeotrope with a boiling temperature of 72.45°C and an ethyl acetate mole fraction approximately equal to 0.5436.
This Demonstration performs the dynamic simulation of a batch rectification of this mixture. Indeed, temperature is plotted versus time for selected values of the initial composition, reflux ratio, and number of theoretical stages.
The still is charged with 1000 kmol of the initial mixture. The vapor rate is assumed constant and equal to 10 kmol/hr. The molar hold-up of all stages and the condenser are 5 and 20 kmol, respectively.
It is found that (1) the first product to exit the column is the azeotrope, which behaves as a pure component; (2) if the initial composition is very rich in ethyl acetate (respectively in ethanol) then this latter component will exit the column once all ethanol (respectively ethyl acetate) has left the column in the form of a binary azeotrope.
If the initial composition is equal to the azeotropic composition, then the temperature remains constant at all times and is equal to the boiling temperature of the azeotrope.
In addition, the separation is improved if one chooses large reflux ratios or a large number of theoretical stages. Otherwise sloppy separation is the result.
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