Steady-State Distillation of a Quaternary Mixture
Consider a distillation column separating a quaternary mixture composed of benzene, toluene, -xylene, and ethylbenzene at . This column has 10 stages, a total condenser, and a partial reboiler. The feed stage location is stage five counting from the top. The feed composition is for each of the four components. You can set the value of the feed vapor fraction, , where is the feed quality. The feed flow rate is set to . The reboil and reflux ratios are both chosen equal to . The Demonstration uses a rigorous approach (solving MESH equations) and displays the composition versus the stage for all four components (benzene in orange, toluene in blue, -xylene in green, and ethylbenzene in red), the temperature profile inside the column, as well as the vapor and liquid flow rates (magenta and blue, respectively). The results obtained are compared with Aspen HYSYS for three selected values of : 0, 0.5 and 1.
 E. J. Henley and J. D. Seader, Equilibrium-Stage Separation Operations in Chemical Engineering, New York: Wiley, 1981.
Expressions for pure component vapor and liquid enthalpies were adapted from Aspen HYSYS.
The mixture is assumed to obey Raoult's law since it is composed of four aromatic compounds at a total pressure of 1 atmosphere.