Multifunctional process unit is an important element in process intensification and reactive distillation is one of the most common examples of multifunctional processes[1]. Despite recent progress in understanding the feasibility, design, and, in some cases, control of reactive distillation[2], conceptual design of reactive distillation is still carried out in an ad hoc manner and the process flowsheet seems to vary from case to case. Even for the same process (e.g., ethyl acetate and butyl acetate), literature examples also show several different process configurations [3]. By process configuration, we mean the relative position of the reactive zone, and separation sections. In other words, a systematic design procedure which is capable of covering a wide range of system parameters is lacking. The objective of this work is aimed to provide a systematic design procedure to determine the process configuration. Instead of investigating real chemical systems, ideal chemical reaction systems with different relative volatility rankings will be studied[4-6]. This provides a gradual transition as the reaction and separation properties change. The reaction considered is a reversible reaction, A+B=C+D, and this constitutes a quaternary system with 24 (4!) possible relative volatility arrangements. These 24 systems can further be grouped into six categories according to the ranking of relative volatilities of reactants and products. The likely process configurations will be explored and design will be optimized based on the total annual cost (TAC). The results clearly indicate that the relative volatility rankings play a dominant role in the reactive distillation configuration and the TAC varies by a factor of ~10 as we move from the most favorable case to the least favorable relative volatility ranking. Finally, heuristics are given to correlate the relative volatility ranking to the total annual cost.

Keywords: reactive distillation, process configuration, relative volatility, conceptual design

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