We next consider an example that is more difficult to solve. We want to separate a quaternary mixture consisting of Ethanol, n-Propanol, i-Butanol and n-Butanol in a dividing wall column with two dividing walls as shown in Fig- . This system was suggested in literature to be suited for the considered mDWC Preißinger, Ränger, and Grützner 2019. Again the vapor liquid equilibrium is modeled using the NRTL-model and the corresponding parameters are given in A. The distillation column has a total height of 78 theoretical stages and is operated at a constant pressure of 1 bar. The separation is performed in a distillation column with two dividing walls. The first dividing wall splits the stages 14 to 52 an the second splits the stages 40 to 65. The second dividing wall is located to the right of the first dividing wall. The feed is located on stage 40. We consider a feed of 100 mol/h and molar concentrations of 1/4 mol/mol for each component. We try to minimize the reboiler duty QR and demand the purities of 0.98 mol/mol in the product streams. The different sections of the column organized as Petlyuk sequence are shown in Figure . The product streams are denoted by A-D. The streams connecting the different sections are numbered by 1 to 16. As in the previous example, we will first present the results obtained with the new approach and then compare them to results obtained with Aspen Plus R as black box simulation software.