Speaker
Description
The thermo-chemical conversion of coke and reduction of iron ore particles both depend on mass transport from the bulk fluid phase towards the reactive sites in the solid phase. Pore diffusion limits this mass transport in porous particles at intermediate temperatures, while chemistry is limiting co
nversion rates at low temperatures. Besides temperature, pore diffusion rates also depend on physical particle properties, e.g. pore diameter, tortuosity, fluid properties, and species gradients. Modeling approaches of different complexity for pore diffusion can be found in literature. Their diffusion rates can vary by orders of magnitude. Thus, the right choice of diffusion model is highly important for reasonable predictions. The wrong choice can lead to large under/over estimations of conversion or reduction rates.
We conduct a numerical study of the effects of different diffusion models on the conversion of a single fuel particle to evaluate their suitability for metallurgical applications. The numerical model we employ is fully implemented in the open source CFD package OpenFoam®-7. The inside of the solid fuel particle is modeled using an Euler-Euler approach, which implies that the particle pores are not resolved. The particle and surrounding fluid are coupled using explicit Robin-Neumann-coupling for species concentrations, pressure, and temperature.
In this work, we will briefly introduce the different diffusion models and their characteristics, followed by an explanation of the setup of our numerical experiments. Finally, the different diffusion models will be evaluated in regard to their quality of prediction compared to experiments available in literature, and their computational cost.