Simple Batch Distillation of an Ethanol-Water Mixture
An equimolar binary mixture of ethanol and water is to be separated in a still pot, which initially contains 0.575 kmol of the mixture. You can set the operating pressure, , of this simple batch distillation experiment, where can vary from 700 to 900 mmHg so that the ideal gas-phase assumption holds.
This Demonstration plots the temperature of the liquid in the still, , and the temperature of the distillate (i.e., condensed vapor exiting from the still), , versus time (green and magenta curves, respectively). As expected, lags behind because the distillate is richer in ethanol.
In addition, you can see the plots of the composition in the still, , and in the distillate, . For this transient problem, computations include both the mass and the energy balance equations. For higher total pressure values, the temperature profiles are shifted to higher values. A constant-heating policy of the still pot is used with .
With the simple experimental apparatus shown below, one can obtain the temperature in the still pot, , and that of the escaping vapor, . Since the system is a binary mixture, the composition in the still pot can be inferred from the temperature measurement obtained using a thermocouple with digital display.