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Optimal Operation and Feedback Control of Reactive Batch Distillation In Middle-Vessel Columns

Harvey Arellano-Garcia, Irisay Carmona, and Guenter Wozny. Chair of Process Dynamics and Operation, Berlin Institute of Technology, Str. des 17. Juni 135, 10623, Berlin, Germany

The transient nature of batch distillation allows for configuring of batch columns in a number of different ways. In particular, when chemical reactions and physical separations have some overlapping operating conditions the combination of these tasks in a single process unit can offer significant benefits.

In this work, we present the optimal operation and feedback control of a new operation mode for reactive batch distillation in middle vessel columns. For this purpose, the feed mixture is loaded into the middle vessel between the two separation sections, and the products are simultaneously obtained from the top and the bottom of the column reducing the way of separation. The special feature of this novel operation mode lies on the fact that depending on the characteristics of the reaction mixture, the reaction will also take place either along the upper column or along the lower column. In the former case, the reaction will be enhanced by adding one of the educts into the top of the column. In the latter, the educt feed will be supplied to the reboiler of the lower column, and the most volatile components will be evaporated out of the lower column towards the upper column through a vapour bypass configuration during the batch. Thus, the efficiency of reactive batch distillation can be improved, e.g., less batch time and energy consumption and more product amount.

The operation and control performance of the new operation mode is studied through simulation of two industrial reactive batch distillation processes. The first case study is a trans-esterification of two esters and two alcohols. To simulate both processes, a dynamic rigorous detailed model is used. Comparisons of the new operation mode with the conventional options clearly indicate the improvement by the new operation mode.