Numerical Modeling and Optimization of an Entrained Particle-flow Thermochemical Solar Reactor for Metal Oxide Reduction

The endothermic thermochemical process of metal oxide reduction in an indirectly-irradiated particle-laden flow solar reactor was modeled and analyzed using computational fluid dynamics (CFD) tool Ansys-Fluent. CFD modeling includes chemically reactive multiphase flow including solid-gas interactions, radiation heat transfer among particles, inner reactor walls and gas phase, and particle surface reaction chemical kinetics. A novel indirect heating cavity-type tubular solar reactordesigned for continuous metal oxide reduction was simulated for predicting the temperature distribution profiles and benchmarked with on-sun testing results under similar conditions. Further, design optimization on cavity size was performed for the targeted reaction temperature with enhanced handling capacity. A 50 mm cavityheight was found to be suited for required temperature of above 1900 K for zinc oxide thermal reduction. Prior to reaction kinetics implementation, the study of inert particle case was carried out to understand the influence of particle heating on thermal profile. Finally, reactive particle-laden flow was simulated using Eulerian-Lagrangian combined approach.The chemical conversion efficiency of the ZnO reduction process and the solar-to-chemical energy conversion efficiency were also calculated for varied inlet particle massflow rates.