For a stage k in a conventional distillation column there is a liquid stream (with molar flow rate L k and molar concentrations x k ) flowing from it to the stage beneath and a vapor stream (with molar flow rate V k and molar concentration y k ) flowing from it to the stage above. Likewise, there is a liquid stream and a vapor stream flowing onto it. The equations used to describe their dependency are the MESH equations stated in the following for N C components: