Critical Assessment of P₂O₅ Activity Coefficients in CaO-based Slags during Dephosphorization Process of Iron-based Melts

According to the experimental results of hot metal dephosphorization by CaO-based slags at a commercial-scale hot metal pretreatment station, activity \( a_{{{\text{P}}_{ 2} {\text{O}}_{ 5} }} \) of P₂O₅ in the CaO-based slags has been determined using the calculated comprehensive mass action concentration \( N_{{{\text{Fe}}_{t} {\text{O}}}}^{{}} \) of iron oxides by the ion and molecule coexistence theory (IMCT) for representing the reaction ability of Fe _t O, i.e., activity of \( a_{{{\text{Fe}}_{t} {\text{O}}}}^{{}} \). The collected ten models from the literature for predicting activity coefficient \( \gamma_{{{\text{P}}_{ 2} {\text{O}}_{ 5} }} \) of P₂O₅ in CaO-based slags have been evaluated based on the determined activity \( a_{{{\text{P}}_{ 2} {\text{O}}_{ 5} }} \) of P₂O₅ by the IMCT as the criterion. The collected ten models of activity coefficient \( \gamma_{{{\text{P}}_{ 2} {\text{O}}_{ 5} }} \) of P₂O₅ in CaO-based slags can be described in the form of a linear function as \( \log \gamma_{{{\text{P}}_{ 2} {\text{O}}_{ 5} }} \equiv y = c_{0} + c_{1} x \), in which independent variable \( x \) represents the chemical composition of slags, intercept \( c_{0} \) including the constant term depicts temperature effect and other unmentioned or acquiescent thermodynamic factors, and slope \( c_{1} \) is regressed by the experimental results. Thus, a general approach for obtaining good prediction results of activity \( a_{{{\text{P}}_{ 2} {\text{O}}_{ 5} }} \) of P₂O₅ in CaO-based slags is proposed by revising the constant term in intercept \( c_{0} \) for the collected ten models. The better models with an ideal revising possibility or flexibility in the collected ten models have been selected and recommended.