Finding distillation column sequences for sharp splits of multi-component mixtures that have overall minimum energy consumption is still an important problem, particularly with the rapidly rising cost of energy. While there is a vast literature on the subject for the case of (c – 1) columns, where c is the number of components in the mixture, virtually all papers disregard configurations with more than (c – 1) columns because of the capital costs associated with additional columns.

In this work, we study the problem of finding overall minimum energy sequences for non-interlinked columns using the shortest stripping line distance approach. A theoretical framework as well as applications involving mixtures modeled using a variety of phase models (i.e., constant relative volatility, ideal, non-ideal, and azeotropic behavior) are presented. Numerical results clearly show that the shortest stripping line distance approach can find the most energy efficient column sequence – even in cases where this sequence has more than (c – 1) columns – and thus show that stripping line distance correlates with overall energy consumption for non-interlinked column sequences. These results represent an important first step in defining a new and powerful methodology for energy efficient multi-column synthesis and design. Many geometric illustrations are used to highlight key points of our geometric design methodology. Finally, some additional remarks are made regarding interlinked column sequences.