Design and optimization of thermally coupled distillation schemes for the separation of multicomponent mixtures

The design of thermally coupled distillation sequences for the separation of multicomponent mixtures is complex because of the greater number of degrees of freedom in comparison to distillation sequences based on conventional columns. The energy-efficient design procedure for thermally coupled distillation sequences for the separation of ternary and quaternary mixtures is extended to the separation of five or more component mixtures [Blancarte-Palacios, J. L.; Bautista-Valdes, M. N.; Hernandez, S.; Rico-Ramirez, V.; Jimenez, A. Energy-Efficient Designs of Thermally Coupled Distillation Sequences for Four-Component Mixture. Ind. Eng. Chem. Res. 2003, 42, 5157]. The schemes analyzed (five fully thermally coupled sequences and two partially thermally coupled sequences) include side rectifiers, side strippers, or both types of side columns. The procedure uses initial designs for thermally coupled distillation sequences obtained from the distribution of tray sections of conventional distillation sequences and then optimized for energy consumption using the interconnecting flows as search variables. The methodology provides a robust tool for the design of multicomponent thermally coupled distillation schemes. The proposed design strategy results in thermally coupled sequences that not only achieve the specified separation but also require lower energy consumptions and better thermodynamic efficiencies than conventional distillation schemes.