The general behavior of the paths of distillation of multicomponent mixtures in sections of a complex continuous column is analyzed.

The autoextractive distillation of an azeotropic solvent mixture of acetone, chloroform, n -butanol, and dimethylformamide is considered. A set of flowsheets belonging to different structural classes is synthesized (flowsheets containing two-withdrawal columns and flowsheets involving complex columns with a single side section). The flowsheet that is optimal in energy consumption is revealed, and it is shown that flowsheets with coupled heat and material flows are more efficient than conventional ones.

The possibility of bringing real distillation processes to thermodynamically reversible distillation is considered. Distillation systems involving partially or fully thermally coupled columns are suggested for the separation of ternary mixtures. The transformation of the optimal flowsheet in response to variation of feed composition is studied. Recommendations are provided as to the choice of an energy saving distillation design.

The vector equation of mass transfer in multicomponent systems, the conditions for the existence of singular points, and the temperature distributions along the height of a two-section distillation column are analyzed.

A method based on the representation of flowsheets as graphs is proposed to synthesize flowsheets of extractive distillation of multicomponent azeotropic mixtures in complex columns with partially coupled heat and material flows. It is shown that the flowsheets constructed can provide a significant decrease in the energy consumption for separation because the process becomes structurally closer to thermodynamically reversible distillation.

A multicomponent mass-transfer equation for the distillation of multicomponent mixtures is derived in terms of the thermodynamics of irreversible processes.

An algorithm for synthesizing extractive distillation flowsheets for separation of complex ternary azeotropic mixtures with different vapor-liquid equilibrium patterns is proposed.

A graph method and a matrix method are proposed for synthesizing distillation flowsheets by analyzing process trajectories.

Isocriterial manifolds are derived by comparing the linear distillation flowsheets and analyzed.

Separation flowsheets for three-, four-, and five-component mixtures are considered. Graphs analysis of the arrangement of feed-composition regions is performed to find the optimum separation flowsheet.