Shortcut-based design of multicomponent heteroazeotropic distillation

Abstract:
Shortcut methods are valuable tools in the early stages of chemical process design, where numerous flowsheet alternatives need to be evaluated to determine the most energy-efficient, feasible flowsheet. Various shortcut methods based on tray-to-tray or pinch point analysis for the inspection of feasibility and the determination of the minimum energy demand (MED) for homogeneous azeotropic distillation have been published. For multicomponent heteroazeotropic distillation, however, no generally applicable shortcut methods are available yet. In this work, various shortcut methods for heteroazeotropic multicomponent distillation are assessed. Two novel thermodynamically sound shortcut methods, the feed pinch method (FPM) and the feed angle method (FAM), are proposed to resolve the limitations of existing methods. In particular, the fully algorithmic FAM is applicable to direct, indirect, and intermediate splits for heterogeneous azeotropic mixtures of any number of components. The novel methods are illustrated by four sample separations involving ternary, quaternary and quinternary heterogeneous mixtures. The performance of the FAM is highlighted by an industrial case study, where the effectiveness of an optimization-based conceptual design of a heteroazeotropic column sequence is demonstrated. The computational efficiency of the FAM allows a numerical optimization of the operating points of flowsheet alternatives in order to determine the most energy-efficient variant.

Keywords:
heteroazeotropic distillation, shortcut method, conceptual design, rectification body method, feed pinch method, feed angle method

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