Analyses of CWF (CaFe3O5) phase formation in lime-magnetite pellets

An alternative route of magnetite processing involving the formation of CWF (CaFe3O5/calcio-magnetite) phase in lime-magnetite pellets (LMPs) was proposed in the previous paper. This paper is focused on the isothermal kinetics of the overall reaction, and of CWF formation, at 850, 950 and 1050°C. Different kinetics models were evaluated for the current data, and model-fitting techniques with linear regression analysis was applied. Microstructural analysis was carried out using SEM and EPMA to understand the evolution of product morphology and the reaction mechanism. The time series experiments and characterization results suggested the formation of CWF phase within 5 min of reaction and the formation of C2F (2CaO·Fe2O3) as a transient phase. Kinetic analysis suggested both the overall reaction and CWF formation could be described by Jander model. While there was good evidence for solid-state diffusion-controlled reaction mechanism, further study is required to establish the rate limiting step.