Condensation of P₂O₅ at the Interface between 2CaO·SiO₂ and CaO–SiO₂–FeO_x–P₂O₅ Slag

Abstract

In order to clarify the reaction behavior of phosphorus in the multi phase flux, the solid 2CaO·SiO₂ piece was reacted with the CaO–SiO₂–FeO_x–P₂O₅ slag for 1 to 180 s at 1573 or 1673 K. The interfaces between the original solid and liquid phases were observed and compositions of both phases were analyzed by SEM/EDS.
The result shows that P₂O₅ is condensed at the rim layer of 2CaO·SiO₂ piece very fast in less than 1 s. The P₂O₅ condensed phases are identified as the mixture of 2CaO·SiO₂–3CaO·P₂O₅ solid solution and the surrounding liquid slag. After reaction for longer time, the reaction behavior of P₂O₅ depends on the reaction temperature and initial slag composition. Reaction temperature and mole ratio of CaO/SiO₂ in the initial slag influence the stability of P₂O₅ condensed phases. Higher temperature induces the dissolution of P₂O₅ condensed phases while larger mole ratio of CaO/SiO₂ has the opposite effect.