Numerical investigation of a metal-oxide reduction reactor for thermochemical energy storage and solar fuel production

The optimum design of a thermochemical reactor involves complex phenomena such as radiation heat and mass transfer, reaction kinetics, and fluid-solid interactions which makes the process to be cumbersome. The computational modelling using computational fluid dynamics (CFD) is an important tool to study, analyse, interpret and optimize such a complex system. The present study has developed a CFD model using Ansys-Fluent 14.0. The model employs the Eulerian-Lagrangian approach with the chemical reactions for a vertical axis thermochemical reactor for Zinc oxide reduction process. The conversion efficiency and temperature distributions for Zinc oxide reduction estimated by the CFD results have been validated with the published results by the PROMES CNRS laboratory (France) for a horizontal reactor design. The effect of particle size and gravity with a view to adapt it for a vertical beam-down solar concentrator have been analysed in the present study. It was observed that smaller particles provide higher surface area for enhanced heat transfer. Gravitational effects turned to be significant as the particle size increases. The model will assist in the effort of developing an efficient solar chemical reactor, for innovative thermochemical energy storage systems or fuel production, which will be tested at the Masdar Institute's beam down research facility.