Abstract
The Petlyuk or fully thermally coupled distillation arrangement has the ability to separate a ternary feed into three pure products with an energy consumption 20-30% below conventional arrangements. The most interesting realisation is the dividing wall column (DWC). The Petlyuk arrangement has typically 5 degrees of freedom: Boilup rate, reflux rate, side-stream rate and split ratios above and below the dividing wall. In order to achieve the potential savings in practice, the column has to be carefully controlled.