Work

Combustion of micron-sized iron particles in a drop tube reactor

Year: 2024

Type: article

Abstract: Combustion of micron-sized particles of iron, a promising renewable alternative to fossil fuels, was investigated in a drop tube reactor (DTR) under overall lean conditions (excess air ratio λ in the range of 1.1-1.4). A bimodal particle size distribution was observed after combustion: black micron-sized particles consisting of a mixture of iron oxides, with oxidation degrees ranging from 60% to 90%, and reddish ultra-fine particles of Fe2O3. The oxidation degree of the products showed no obvious variation with the reactor temperature. The coarse product particles were comparable in size with those of the raw iron particles, independent of temperature. A simplified model for the combustion was used to analyze the results. It was based on the Particle Equilibrium Composition approach by Gool et al. (Appl Energy Combust Sci 2023;13:100115) that assumes the oxidation from Fe to FeO to be limited by external diffusion and further oxidation by thermodynamic equilibrium. The model predicted larger oxidation degrees than observed experimentally. The difference was believed to be due partly to short-comings in the modeling assumptions and partly to stratification in the drop tube reactor, resulting in local fuel-rich conditions. The low impact of reactor temperature on the final oxidation stage indicates that diffusion limitations, rather than kinetic barriers, are rate controlling.

Source: Fuel

DOI: 10.1016/j.fuel.2024.133814