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A pressure-driven, dynamic model for distillation columns with smooth reformulations for flexible operation

Hoffmann, Christian; Weigert, Joris; Esche, Erik; Repke, Jens-Uwe

FG Dynamik und Betrieb technischer Anlagen

Dynamic models for plants including the startup or shutdown phase are still scarce as the (dis-)appearence of phases or streams is challenging to implement. We present an approach to model a distillation column, in which these operation modes are also considered without exchanging equations. For this purpose, the well-known modeling equations for distillation columns are reformulated robustly to allow for the disappearance of the vapor phase without discontinuities. The reformulation does not depend on solving an optimization problem and could easily be applied to other column types or different unit operations. The proposed model is solved in two case studies with 10 and 40 trays, respectively. In these case studies, the influence of single phenomena on the obtained dynamic profiles is investigated, e.g., weeping, which are often neglected. The proposed modeling approach yields a dynamic model that can be solved without reinitialization for a realistically large number of trays.