Column Scale-Up

When scaling up a reactive distillation process, the optimum column diameter and height must be chosen. Similarly to conventional distillation, the determination of the required column height is one of the most difficult tasks in process design. In general, it is based on the packing separation efficiency, which is obtained from non-reactive experiments with well-known test mixtures and chemically inert packing. Care must be taken because data from lab scale packing may differ appreciably from the packing applied on the industrial scale. According to Moritz and Hasse [6], the Sulzer Katapak-S has about three theoretical stages per meter on the lab scale, while on the industrial scale, the same packing provides only one to one-and-a-half theoretical stages per meter.

Besides these essential questions various criteria such as location of the reactive zone and catalyst mass must be taken into account. In the case of reactive distillation, the column height is influenced not only by the separation efficiency but also by the required residence time. Further difficulties in scale-up calculations arise from complex mass-transfer phenomena and hydrodynamic effects.

Simulation might be a decisive basis for process design when all major data are present. However, with the current state of the art it is unlikely that any company would build a new reactive distillation without any pilot plant tests or reliable references.

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