CFD‒PBM modeling of gas‒particle reactive flow and particle aggregation in the flash smelting furnace

The aggregation of molten particles in flash smelting furnaces has become a growing concern as feed rates increase, necessitating a deeper understanding to enable practical adjustments. This study presents a coupled CFD‒PBM approach to investigate the gas–particle reactive flow and particle aggregation within the furnace. Based on experimental data, a temperature-based aggregation kernel is developed and integrated into the PBM to characterize particle evolution. The simulations are validated against experimental data, demonstrating reasonable agreement in terms of particle distributed radius and growth rate. Furthermore, the effects of airflow momentum ratio and injected particle size on particle evolution are analyzed. The results reveal that the high-temperature region, generated by the exothermic oxidation of sulfides, begins at the mid-height of the reaction shaft. Within this region, molten particles aggregate and grow to over twice the injected size. Increasing the airflow momentum ratio enhances particle ignition and oxidation, and greater particle dispersion reduces collisions and aggregation. Larger injected particle sizes also decrease aggregation but may delay the particle ignition and oxidation in the middle of the reaction shaft. However, the oxidation rates of larger particles remain comparable upon reaching the settler. These findings suggest that increasing the airflow momentum ratio and the injected particle size improves production efficiency, presenting a practical strategy for optimizing FSF operations.