On the Role of Radial Dispersion in the Behavior of a Cooled Fixed‐Bed Reactor: Numerical Investigation of Fischer–Tropsch Synthesis with a Cobalt‐Based Catalyst

The impact of radial dispersion of both heat and mass on the behavior of cooled fixed‐bed reactors was explored using a two‐dimensional reactor model. This study accounted for dispersion through an effective radial thermal conductivity (λrad) and a radial dispersion coefficient of mass (Drad), with Fischer–Tropsch synthesis serving as an illustrative process example. Under moderate reaction conditions and hence still rather gentle radial temperature profiles, the effect of mass dispersion on reactor performance was found to be minimal, even if disregarded (Drad = 0), whereas dispersion of heat (λrad) always significantly impacts reactor behavior. Nevertheless, for precise thermal runaway predictions by a reactor model, incorporating mass dispersion by a realistic Drad value is essential. A 2D numerical model was used to simulate the impact of radial dispersion on the behaviour of a multi‐tubular Fischer–Tropsch reactor. For a reliable reactor simulation, accurate values of the parameters of radial heat transfer are an absolute must, but rough estimations of radial mass transport should also be included, at least to predict accurately the runaway behaviour.