Interface migration and alloying mechanism of Fe and P for ferrophosphorus alloy production during the carbothermic reduction of phosphorite

Ferrophosphorus (Fe–P alloy), a byproduct in the carbothermal reduction of phosphorite for yellow phosphorus production, has remarkable potential application as foundational precursors to prepare advanced catalysts and energy materials. However, the gas-solid-liquid equilibrium in the reduction smelting of phosphorite and hematite is intricate, and the reduction, volatilization, and alloying mechanisms of Fe and P at higher temperatures should be given close attention to optimize the production of yellow phosphorus vapor and Fe–P alloy. In this study, the reduction smelting behaviors of fluorapatite and hematite in the phosphorite ore were investigated. Carbothermic reduction reactions of Ca5(PO4)3F with and without Fe2O3 are calculated, establishing theoretical fundamentals. The phase and microstructure evolutions of Ca5(PO4)3F and Fe2O3 are researched. This work also emphasizes the interfacial element migration to clarify the reduction, volatilization, and alloying of Fe and P by considering the solid-solid interface of Ca5(PO4)3F–Fe2O3 and the gas-liquid interface of P2 vapor-metallic Fe.