Nonsmooth Model for Dynamic Simulation of Phase Changes

TitleNonsmooth Model for Dynamic Simulation of Phase Changes
Publication TypeJournal Article
Year of Publication2016
AuthorsSahlodin AM, Watson HAJ, Barton PI
JournalAIChE Journal

Dynamic modeling of processes involving phase changes can be challenging due to changes in the model equations caused by appearance and disappearance of equilibrium phases. Dynamic simulation of these processes requires the ability to detect the change in the number of phases and adapt the model to the new phase regime on the fly. In this work, an easy-to-use nonsmooth model for dynamic simulation of processes with vapor-liquid equilibrium is presented. The presented model does not introduce any auxiliary variables or equations, nor does it require solution of an optimization problem to determine the new phase regime during the dynamic simulation. It can therefore be used for comprehensive simulation of, e.g., distillation columns, where the number of phases present can change during startup and shutdown. The nonsmooth model is illustrated through examples of an evaporator and a distillation column.