(184a) Spatially Resolved Fixed-Bed Versus Pseudo-Homogeneous Reactor Models Including a Detailed Reaction Mechanism

Fixed bed or packed bed reactors are widely used in the chemical and process industry amongst others for highly exothermic or endothermic catalytic surface reactions. A small tube to particle diameter ratio (D/d-ratio) facilitates a safe thermal performance of these reactors. Many correlations reported in literature for pressure drop and heat transfer are limited in their predictive capability for such packed bed reactors due to a dominant influence of the confining wall. It affects the porosity distribution and as a result the velocity field as well as the species and temperature distribution within the bed. Accurate measurements for development of new correlations can be cumbersome, expensive and many times inaccurate due to the complexity of the geometry. The increasing power of computational hardware in the last decade has enabled virtual experiments: Computational Fluid Dynamics (CFD) can now be used even for three dimensional spatially resolved investigations of those reactor types including detailed surface reaction mechanisms as recently shown by [Wehinger et al., 2015] for different catalytic particle shapes and by [Eppinger et. al., 2015] for an optimization study on operating conditions. A complete numerical workflow was shown where the packing generation with DEM (discrete element method), the meshing and the simulation were done with the finite volume code STAR-CCM+ by CD-adapco and for the optimization Optimate+/HEEDS by Red Cedar Technology were used.

The current contribution is an extension of our study which was presented at the AIChE annual meeting 2015 ([Eppinger et. al., 2015]) with a focus on a comparison of the spatially resolved packed bed results with the results achieved by a less computational intensive pseudo-homogeneous approach. The significant reduction in calculation time is very attractive for industrial applications, but on the other hand this simplification can lead to inaccuracies. The sensitivity of the yield and conversion on mass transfer limitation which are typically occur in such reactors will be shown and quantified as well as the effect of typically used model enhancements like including local porosity profiles.

References

N. E. McGuire, N. P. Sullivan, O. Deutschmann, H. Zhu, R. J. Kee Dry reforming of methane in a stagnation-flow reactor using Rh supported on strontium-substituted hexaaluminate, Applied Catalysis A: General. (2011), 257-265

G. D. Wehinger, T. Eppinger, M. Kraume. Evaluating Catalytic Fixed-Bed Reactors for Dry Reforming of Methane with Detailed CFD, Chem. Ing. Tech. (2015), 734-745

T. Eppinger, N. Jurtz, R. Aglave, Gregor D. Wehinger, M. Kraume. A Numerical Optimization Study on the Catalytic Dry Reforming of Methane in a Spatially Resolved Fixed-Bed Reactor, AIChE Annual Meeting 2015, Salt Lake City, USA