Process Evaluation by Dimensionless Numbers

For the reliable prediction of RD process performance it is crucial to identify the dominant local mass and energy transport resistances between the phases in a packed catalytic column section. Dimensionless parameter groups are an efficient tool for this purpose, which allow estimation of the relevance of certain transport resistances from experimental data. Here only the most important qualitative results are given [33]. 

As already used in the preceding subsections, the Damkohler number Da evaluates the effective rate of the chemical reaction in comparison to the feed flow rate 

kf represents the effective reaction rate constant including internal transport resistances of the catalyst packing. stands for the catalyst volume installed in the column. For Da 3 1 the chemical reaction approaches chemical equilibrium, for Da 1 the reaction is far from its equilibrium. 

Since the separation in distillation columns is dominated by the vapor-liquid equilibrium, it is a reasonable assumption to neglect the mass-transfer resistances between the vapor phase and the liquid phase. However, in RD columns, the importance of vapor-liquid mass-transport resistances depends on the following dimensionless ratio 

Internal mass transport inside the catalyst particles should be evaluated with the help of the Thiele modulus 

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