Title: The implementation of detailed heterogeneous chemistry inside CFD-DEM modeling of gas-solid fluidized beds
Author list: Florian Wery, Laurien Vandewalle, Geraldine Heynderickx, Kevin Van Geem Key words: Heterogeneous catalysis, microkinetic modeling, CFD-DEM, fluidized bed Abstract text (under 300 words):
Many innovations in chemical industry rely on the accurate modeling of different phenomena inside the reactor. Hereby, Computational Fluid Dynamics (CFD) simulations play an important role in efficiently testing and benchmarking new possible reactor geometries. Due to the ever-increasing computational power, new doors are opened facilitating a first-principle approach at every scale combined into one multi-scale model.
For many catalytic processes, gas-solid fluidized beds are preferred over packed bed reactors, mostly because of their excellent heat transfer and mixing characteristics. Two different techniques exist for modeling gas-solid systems. Euler-Euler models treat the gas and particle phase as interpenetrating continua, requiring (empirical) closure models. Euler-Lagrangian models on the other hand, track particles explicitly, resulting in a higher accuracy at the cost of higher computational efforts.
In this work, a reactive compressible four-way coupled CFD-DEM solver was developed with the open- source package CFDEMcoupling, which couples the CFD package OpenFOAM with the DEM solver LIGGGHTS. A heterogeneous catalytic framework was implemented including both surface and gas- phase chemistry, including models for gas-solid mass and heat.
In a first step, hydrodynamic studies were performed to validate the solver under non-reactive conditions, by comparison with experimental PIV images. The reactive framework was then used to simulate reactor geometries for the Oxidative Coupling of Methane (OCM), one of the most promising direct technologies to convert methane into ethylene. For reactive validation, our experimental packed bed set-up was simulated with an in-house microkinetic model, comprising of 39 gas phase and 26 catalytic reactions, between 24 gas phase and 11 surface species. The results of these simulations were compared to both experimental data and pseudo-homogeneous 1D PFR simulations, to which good agreements were found. As a proof-of-concept, the validated reactive CFD-DEM framework was applied to simulate a larger-scale fluidized bed reactor for OCM.
