Scaling down of trickle-bed reactors

It is possible to obtain kinetically representative data in very small laboratory reactors if the temperature and concentration gradients on the scale of the catalyst particle are absent. The bed needs to be isothermal and the reactor should behave as a plug-flow reactor. These requirements imply using small particles and a sufficient bed length. For flow through such small particles, surface tension forces become much more important, and established trickle-bed correlations cannot be extrapolated. For a reliable design of the reactor bed and for a choice of window of operation, the hydrodynamics of such fixed-bed microreactors have to be investigated. 

In principle there are the following alternative ways to scale down the industrial trickle-bed reactors down-scale according to geometric similarity, industrial reactor representation by 

3 Maintenance of the fluid dynamic similarity Industrial reactor represented by an integral laboratory reactor 

As long as the fluid dynamics and reaction kinetics are closely interconnected so that their effects on the chemical reactions are inseparable, the only mode to scale down an industrial reactor to an integral laboratory reactor is to reduce the reactor diameter and keeping the same length. Thus, the flmd dynamic similarity is maintained (if the diameter is not reduced beyond the limit set by the wall effects), and the experiments are carried out not only at the same space velocity as in the industrial situation but also at the same liqmd and gas linear velocities. This approach is based on the idea that in the industrial reactor the behavior in a horizontal plane within the bed is the same 

In the phenomenological approach an attempt is made to isolate the various phenomena that affect the apparent reaction and to establish the appropriate correlations for each of them (assuming separable mechanisms). An example is the reactor models in which it is assumed that the reaction is pseudohomogeneous and the phases are in plug flow. For a first-order reaction one may write [113] 

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