Using the improved starting values, we can proceed with the actual optimization by introducing the minimization of the reboiler duty as an objective. As before we first used the additional inequalites given in Equations ( ) and ( ). The calculation terminated successfully after 56 iterations (25.23 seconds). The product streams of the obtained solution are given in Table . Additionally, values for the reboiler duty as well as the split ratios are given. Where v s,1 and v s,2 are the ratios of vapor that flows to the right of the first and the second dividing wall. The ratios of liquid that flows to the right of the dividing walls is denoted by l s,1 and l s,2 .