A Note on the Controllability of Two Short-Cut Designs for a Class of Thermally Coupled Distillation Sequence

Abstract

The separation of multicomponent mixtures with conventional distillation sequences is energy-intensive. The use of thermal coupling sequences provides a more-efficient alternative, although their industrial usage has been quite limited, because of the complexity of design methods and potential difficulties during operation. In this work, we study a direct thermally coupled sequence for the separation of ideal ternary mixtures and perform a comparative study of two different designs, one based on the tray structure of an equivalent conventional sequence and the other specifically considering the effect of the thermal coupling on tray distribution and operational flows. Using the singular value decomposition technique on open-loop transfer function matrixes, controllability indexes were obtained. The controllability indexes of both designs are of the same order of magnitude, which means that their dynamic responses are basically the same. Although additional studies of dynamic simulation under closed-loop conditions are necessary, our results indicate that the controllability properties are similar, and that the design that provides the smallest energy consumption should be favored.