Synthesis of distillation column configurations for a multicomponent separation

Thermally linked distillation column configurations to separate near-ideal multicomponent mixtures containing four or more components are discussed. It is shown that for sharp separation of an n-component mixture using only one reboiler and one condenser the minimum number of rectifying and stripping sections needed is 4n - 6. A stepwise procedure is proposed to obtain such distillation configurations, and a series of observations are presented which make the task of generating these configurations a little easier. It is found that, for n greater than or equal to 4, some of these distillation configurations are missing from the known superstructures in the literature. An alternative method is proposed to obtain an n-component superstructure. The resulting superstructure has all the earlier known configurations embedded within it and contains the substructures incorporating the missing configurations. This provides a more complete superstructure for the optimization task.