Rate of 2CaO·SiO₂ Dissolution into Molten CaO–FeO–SiO₂ Slag Saturated with Solid Iron

Abstract

Rate of 2CaO·SiO₂ dissolution into molten CaO–FeO–SiO₂ slag saturated with solid iron has been investigated considering the promotion of lime fluxing. A new diffusion couple method has been applied where 2CaO·SiO₂ pellet was immersed into molten CaO–FeO–SiO₂ slag in an iron crucible, slag convection being suppressed. Concentration profile of components was observed and the diffusion behavior was well understood. Considering the pseudo-binary inter-diffusion between components such as CaO and SiO₂ and slag phase matrix, diffusivity of CaO and SiO₂ in the present slag has been determined to have the values from 4.9×10⁻⁷ to 4.7×10⁻⁵ cm²/s at temperatures from 1573 to 1673 K. Assuming the dissolution mechanism as continuous formation and dissolution of 2CaO·SiO₂ on the surface of CaO, complete dissolution time into the flowing slag has been estimated on the basis of the Ranz-Marshall empirical equation, and temperature is found to be controlling factor of the dissolution rate in the normal operation condition.