Phosphorus exhibits considerable segregation in steelmaking slag. In order to recover phosphorus from slag to K3PO4 via molten iron, a carbothermic reaction using microwave heating was suggested recently. The carbothermic reduction of phosphorus from slag to molten iron using microwave heating was carried out at 2073K. However, at this temperature the thermodynamic properties of both slag and molten iron cannot be determined experimentally. Therefore, the computational approach of the so-called CALPHAD method is very useful to understand the transfer of phosphorus from slag to metal and to enhance this reaction. In the present investigation, a theoretical study of the reduction behavior of phosphorus in slag was carried out at much lower temperatures using the recently developed thermodynamic database in the FactSage program. The calculated results showed reasonable accordance with the experimental data; namely, the thermodynamic database could be applied successfully to higher temperature reactions. The current study found that higher temperature and high SiO2 concentration are favorable for the recovery of phosphorus from slag.

As environmental concerns become a critical issue in the sustainability of the steel industry, manufacturing of various kinds of glass-ceramics and related functional materials recycled from post-mortem slags has become an important topic of research. The slag composition, which was reduced and cooled using this secondary treatment is affected by the operating parameters and thermo-physical properties of the slag, and thus can provide the potential for utilization in highly value-added products such as Portland cement and high-alumina cement. To increase the applications of the reduced slag product, a new cement material as well as slag aggregates from the EAF slags were developed by controlling the composition and morphology through novel methods.