Pyrite roasting in modified fluidized bed: Experimental and modeling analysis

Abstract

In this study, a modified fluidized bed reactor was used to roast pyrite concentrate (PC). To analyze the pyrite conversion and fluid flow in the bed, a 2D model incorporating the Euler–Euler method and the conservation equation of chemical species was employed. In addition, the reactant and product samples were characterized through X-ray diffraction (XRD), X-ray fluorescence (XRF), particle size distribution, and thermogravimetric analyses (TGA). The kinetic parameters of the pyrite decomposition were also determined. The isoconversional method was used to determine the activation energy, pre-exponential factor of the specific reaction-rate equation, and reaction mechanism from thermogravimetry results. This rate law was then applied in the model to account for the depletion of pyrite in the modified fluidized bed. The main crystallographic phase in the formed product was hematite. XRF and TGA result indicate that the PC had high purity and roasting occurred at a conversion of 80 %. The pyrite decomposition kinetics showed activation energy varies from 33.2 to 281.4 kJ∙mol−1 depending on the stage. The kinetic analysis of roasting and its implementation in the model demonstrated that the simulation achieved 72 % PC conversion into the products. These results validate the experimental conversion, illustrating the compatibility of the model with the experimental data. Specifically, the coupling of the rate law from TGA with the dispersed-phase velocity vector encourages to new research possibilities in this field of chemical engineering.