Study of the ammonia oxidation process on platinum gauze and catalyst degradation phenomenon – CFD simulation with surface reaction kinetics and catalyst entrained particles motion and deposition tracking

Abstract

This study is focused on the Computational Fluid Dynamics (CFD) simulation of the Ostwald process using implemented surface microkinetics of ammonia oxidation and applying this model to investigate the catalyst gauze’s degradation issue, a severe problem occurring due to the harsh process conditions. The results allow an in-depth investigation into the surface reaction rates or product selectivity and their gradients on the subsequent layers for a three-layer platinum woven gauze. The authors investigated the effects of critical parameters, such as contact time and gauze temperatures, on product efficiencies, concentrations and surface parameters. The simulation was validated using the experimental data from the literature. The obtained model was used to compute entrained particle trajectories, the efficiency of the recapture of the catalyst gauze’s subsequent layers and identify the spots of the platinum deposition for different catalyst gauze geometries, contact times and entrained particle sizes. Based on the results and literature reports, the authors estimated the spots of the increased platinum release. The discrete phase model (DPM) was used to track the motion of entrained particles, and the accretion model was used to locate the deposition areas. The obtained results agree with the experimentally observed deposition trends described in the literature.