Comparison of particle-resolved direct numerical simulation and 1d modelling of catalytic reactions in a packed bed

Abstract

The work presents a comparison of catalytic gas-solid reactions in a packed bed as simulated on two widely different scales: direct numerical simulation (capable of accurately predicting transfer phenomena in and around a few particles) and 1D modelling (capable of engineering simulations of industrial scale reactors). Particle-resolved direct numerical simulation (PR-DNS) is performed on a small geometry containing ~100 realistically packed monodisperse spherical particles generated via the discrete element method (DEM). These results are compared to a 1D packed bed reactor model using the effectiveness factor approach to account for intra-particle mass transfer and a suitable closure for gas-particle heat transfer. The differences between the results from the two modelling approaches are quantified over a range of Thiele moduli, Prandtl numbers and reaction enthalpies. Results showed that existing 1D-model closures perform well for a simple first order catalytic reaction. Heat transfer completely dominates the overall reaction system when large reaction enthalpies are simulated, while mass transfer limitations dominate at low reaction enthalpies. Future work will extend this comparative approach to packings with more complex particle shapes and complex reactions.