Consider a steady-state ternary mixture of benzene (), toluene (), and -xylene () at . This mixture, with a thermal quality equal to 1.0 (i.e. saturated liquid), is fed to a 19-stage column with a total condenser and partial reboiler. The feed is at stage 10. The feed flow rate is set to . You can set the values of the reflux and reboil ratios ( and , respectively). This Demonstration computes the temperature and composition profiles using a rigorous approach, which includes both the energy and mass balances. The blue, magenta, and brown curves, shown in the composition profile, correspond to benzene, toluene, and -xylene compositions, respectively. For and , the results found in the present Demonstration show good agreement with those given by HYSYS (http://www.aspentech.com/hysys/). HYSYS data is shown with colored dots. The calculation of enthalpies can be improved by taking temperature-dependent heat capacity, for example.