High-temperature carbothermal reduction of phosphate rock: Reaction behavior, kinetics, and molecular dynamics insights

Abstract

The production of P 4 is highly energy intensive, making improvements in the carbothermal reduction efficiency of phosphate rock essential for reducing reaction time and thermal demand. In this study, the high-temperature carbothermal reduction behavior of phosphate rock with silica and coke was systematically investigated from 1300 to 1750 °C through laboratory scale experiments, phase characterization, kinetic analysis, and molecular dynamics simulations. As temperature increased, the phosphorus reduction efficiency rose substantially, reaching 99.17% after 10 min at 1750 °C. Kinetic analysis showed that the reduction behavior at each investigated temperature was well described by a first-order model, with an overall apparent activation energy of 214 kJ/mol under the present experimental conditions. In addition, SiO 2 increased the phosphorus reduction efficiency. Increasing temperature promoted the formation and melting of calcium silicate phases, thereby improving interfacial contact and mass transfer within the reaction system. Molecular dynamics simulations revealed the formation of [SiO 4 ] tetrahedral units and relatively high Ca 2+ mobility. Taken together, the results suggest enhanced local association between Ca 2+ and [SiO 4 ] units, consistent with calcium redistribution and calcium silicate formation. Overall, this study clarifies the high-temperature reduction behavior and mass transfer mechanism of phosphate rock and provides a kinetic and mechanistic basis for developing efficient thermal phosphorus production processes.