Detailed analysis of the particle residence time distribution in a pressurized drop‐tube reactor

Solid fuel conversion in a pressurized drop-tube reactor is studied in detail using a three-dimensional computational fluid dynamics (CFD) model. The main focus is on analyzing individual particle trajectories and residence times, as these data are crucial for the precise experimental estimation of heterogeneous reaction kinetics. The numerical results were substantiated by radioactive tracer measurements carried out in different operating conditions. The numerical results reveal a complex gas flow that is affected by buoyancy due to a non-homogeneous temperature distribution, which has a strong affect on the trajectories of particular particle size fractions. In this case, empirical residence time correlations for particles, as commonly used for the evaluation of heterogeneous kinetic measurements, lose their validity since the assumption of a plug flow is no longer valid. It can be shown that if CFD-assisted data evaluation is used, a significant improvement in the measured heterogeneous reaction kinetics is feasible.