Modeling of homogeneous reactive separation processes in packed columns

The coupling of physical separation and chemical reactions in one unit oper ation, the so-called reactive separation processes (RSPs), are of increasin g interest for scientific investigation and industrial application. RSPs te nd to be very complex due to strong physico-chemical interactions, and a nu mber of the model assumptions that are adequate for traditional unit operat ions may not be suitable in this new context. Models used to simulate RSPs should therefore be highly accurate in order to reflect this complexity. On the other hand, it is not always economical nor feasible to use the most s ophisticated models for a range of different applications, such as process and equipment design, the determination of optimal operating policies, mode l-based control, etc., and the model complexity has to be adapted to the pu rpose. In many cases however, it is not evident which simplifications are a ppropriate, so that the uncertainty concerning adequate ways to model RSPs is still significant. Kreul et al. (1996a, b) have published a very detaile d rate-based model and first simulation results for RSPs including reaction kinetic terms in the bulk and the film areas. In this paper, a detailed mo del investigation is presented, as well as a systematic deduction of possib le model simplifications. The completely kinetic model and the correspondin g equilibrium stage model are applied to various homogeneously catalyzed re active distillation and reactive absorption processes. A number of simulati on results are presented for four very different test systems. It is conclu ded that equilibrium and rate-based approaches can lead to significantly la rger differences in calculated concentrations profiles for RSPs than for no n-reactive operations, so that the additional effort of more complex modeli ng may be justified. In addition, it is demonstrated that if the kinetics o f the mass and energy transfer between the phases are calculated explicitly , in most cases the consideration of interaction phenomena such as diffusio nal and direct reaction-transfer interaction is not necessary. (C) 1998 Els evier Science Ltd. All rights reserved.