Example: Hexane-Ethanol Flash Drum¶
Problem Statement¶
A 200 kg-mol/hour liquid ethanol/hexane mixture that is 20 mole % hexane needs to be separated. Experimental vapor/liquid equilibrium data measured at 1 atm is available in the accompanying chart (from http://www.ddbst.com/en/EED/VLE/VLE%20Ethanol%3BHexane.php)
- What are the bubble point and dew point temperatures and compositions for this mixture?
- Sketch a flowsheet for an isothermal flash drum operating at 1 atm that separates the mixture into liquid and vapor streams of 100 kg-mol/hour each. What fraction of the hexane is recovered in the vapor stream?
- Modify your design so that the vapor stream is 50 mole % hexane. Now what fraction of the hexane is recovered in the vapor stream?
\begin{align*}
200\,\frac{\mbox{kgmol}}{\mbox{hr}} & = F \\
& = L + V \\
& = L + 0.233L \\
& = 1.233 L
\end{align*}