A View of Reactive Distillation Process Design

We close with some comments on the use of these models in RD process design. There are many different types of model now available in the literature for screening, analysis, design, and optimization of RD columns. Below is an outline of a stepwise approach to RD process design  

The design of the equipment for the non-reactive sections should not pose too great a challenge since existing methods of estimating efficiencies or HETP that are based on key-components could be used. For the reactive section, however, the estimation of HETPS and efficiencies is more problematic. There is no easy way to identify key components. Chemical reactions influence component efficiencies in an unpredictable manner (Fig. 9.22 in [1]). Of course, like the rest of the RD community, we could behave like ostriches and bury our heads in the sand while assuming equal component efficiencies (say, 70%) for individual species and hope for the best  

Column hardware choice can have a significant influence on the conversion and selectivity such aspects can be properly described only by the NEQ cell model, or by a still more sophisticated model based on computational fluid mechanics (such models have yet to be developed). It is insufficiently realized in the literature that, say, for tray RD columns, the tray design can be deliberately chosen to improve conversion and selectivity. Even less appreciated is the fact that the design methodology for RD tray columns is fundamentally different from that of conventional trays. Liquid residence time and residence time distributions are more important in RD. The froth regime is to be preferred to the spray regime for RD applications this is opposite to the design wisdom normally adopted for conventional distillation. For relatively fast reactions, it is essential to properly model intra-particle dif 

Besides more research on hydrodynamics and mass transfer, there is a need for more experimental work with the express purpose of model validation. In such process studies, parameters need to be measured along the height of RD columns. Too often measurements are confined to feed and product stream conditions. Such data cannot serve as a reliable discriminant of computer-based process models. 

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