ANALYSIS OF TRACER EXPERIMENTS FROM COMMERCIAL-SCALE TRICKLE-BED REACTORS

Tracer experiments were conducted in commercial-scale trickle-bed reactors (catalytic hydrodesulfurization) to investigate uniformity of liquid and gas distribution in the catalyst bed. Carbon-14 tagged normal paraffins of 8, 16, and 32 carbon atoms were used as tracers to develop residence time distribution curves. Since dispersion caused by maldistribution is difficult to differentiate from spreading due to catalyst diffusion in a heterogeneous system, a model was developed to uncouple the effects. The flow model consisted of two zones with unequal mass fluxes, but otherwise ideal plug flow. The equations describing the transient tracer response were solved by numerical Laplace transform inversion and the split of mass flux to each zone was adjusted to match model output to the experimental data. The impact of the flow distribution on reactor performance was estimated by coupling a kinetic model to the flow model.