Combining Conceptual and Detailed Methods for Batch Distillation Process Design

The separation of multicomponent mixtures by batch distillation generally requires the sequential processing of several splits in one column. The sequencing of the splits and the choice of the column configuration, e.g. regular or inverse column, has a substantial impact on the economic potential of the process. Beside these structural design decisions the profitability of the process is further governed by the transient profiles of the control variables, mainly the vapor boil-up rate and the reflux ratio. The large variety of structurally different operational strategies results in a computationally demanding discretecontinuous dynamic optimization problem. In this contribution, we present how a fast conceptual design method based on the rectification body method (RBM) for the design of continuously operated columns can be utilized to significantly improve the performance and robustness of rigorous optimization-based design methods. It is used to exclude economically unattractive splits from the superstructure for the dynamic optimization problem and to provide an initialization for the dynamic optimization including time-varying initial profiles for the control variable profiles. The approach is illustrated with a zeotropic quaternary mixture.