Analysis of the zone connecting consecutive sectors in distillation columns by the Ponchon-Savarit method

McCabe-Thiele and Ponchon-Savarit methods are two classical graphical methods for the design of binary distillation columns very useful for didactical purposes and for preliminary calculations. Nevertheless, their description in the literature is not complete and not all the cases are analysed. To complete the academic literature dealing with this subject we have generalized equations for the operating lines or DP that define the change between two consecutive sectors ΔkC for any feed condition, together with the different possibilities to extract products or to add or remove heat. A consistent analysis of what may happen when changing between sectors in the column is presented.