Modeling Drainage in Periodic Separation

Simple models are developed for realistic operation modes of periodic separation. The models comprise instantaneous, simultaneous, and sequential draining. Using our models, the influence of a finite drainage time on separation performance is investigated. Linear case systems are modeled for stationary profiles for both simultaneous and sequential liquid drainage. Performance measures, such as tray efficiencies and mass transfer, are compared for different cases using a consistent modeling framework. We find that draining periods – in general – should be minimized, irrespective of the operating mode. For columns with a few stages, the simultaneous draining is most efficient. With a few stages, the differences are negligible. For higher numbers of stages, the sequential draining becomes superior, partially due to the enabling of mass transfer during draining. Two detailed study cases are provided.