DEM-based model for steam methane reforming

Abstract

This work is devoted to the development and validation of a new 3D DEM-based (Euler–Lagrange) model for the steam reforming of methane in a tube filled with spherical catalyst particles (Ni/α-Al2O). The new model includes five gaseous chemical species (CH4, CO2, CO, H2O, H2). The model uses reaction rate expressions taken from the literature (Langmuir–Hinshelwood-Hougen-Watson (LHHW) kinetics). The main novelty of the model is its ability to account for the intraparticle heat and mass transfer for each individual particle coupled with the heat and mass transfer between the particles and the bulk flow. The model is validated against results from a comprehensive particle-resolved 3D-CFD-based model published in the literature. This 3D benchmark case corresponds to a 0.7 m length of packed tube, that consists of 807 spherical catalyst particles at a tube-to-particle diameter ratio of N=5.96. The comparison between our DEM-based model and 3D benchmark results demonstrates a good agreement comprising of 4 K (1%) difference in the temperature of outflow gas phase and up to 3% differences in the composition of outflow gas. Additionally, this new model is compared with a partial equilibrium model, which uses chemical equilibrium inside the catalyst particles and mass transfer rates between the particle surface and gas flow to calculate the reaction rate expressions. The performances of these new models are illustrated using additional simulations for the same packed bed taking into account thermal radiation. Finally, we validate our model against 2D simulations of an industrial scale reformer-tube published in the literature. Good agreements were demonstrated.