This simulation shows how to determine the number of equilibrium stages needed for a two-component (methanol/water) separation in a counter-current distillation column. It also shows the optimal location to feed the binary mixture into the column. Check “view process flow diagram” to show the x-y diagram on the left and the process flow diagram on the right. When that box is not checked, a larger x-y diagram is shown and you can move the cursor over the curves to see labels. The column feed has a methanol mole fraction of z_F = 0.5 and a quality of 0.5. The condenser is a total condenser, so it is not considered an equilibrium stage. Set the external reflux ratio L/D, as well as the methanol mole fractions in the distillate x_D and bottoms x_B streams, with sliders. The number of stages is determined by stepping off stages starting at x_D ; the partial reboiler is an equilibrium stage. The number of equilibrium stages depends on the compositions of the exiting streams and the reflux ratio. The stages can be numbered with the first stage above the reboiler (bottom to top) or with the first stage at the condenser, use buttons to switch between these numbering options. Note that the x_B determined by stepping off stages is often lower than the desired because reaching the exact value of the desired x_B would require a partial stage, which is not possible.

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About:

This simulation was made at the University of Colorado Boulder, Department of Chemical and Biological Engineering.  Authors: Neil Hendren, Rachael L. Baumann

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