An Assessment of the General Applicability of the Relationship Between Nucleation of CO Bubbles and Mass Transfer of Pho
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RE REVIEW
DEPHOSPHORIZATION of hot metal has been studied extensively from the perspective of phosphate capacity of slag and phosphorus partition ratio between hot metal and slag, including Na2O slag systems and CaO-based slag systems as well as calcium sulfate flux.[1–7] Based on a thermodynamic equilibrium approach, these studies have fully investigated the effect of different slag components on phosphate capacity and phosphorus partition ratio under a wide range conditions. Studies correlating phosphate capacity of slag with optical basicity have been reviewed by Mills.[8] Mori[9] derived an empirical equation to describe the relationship between phosphate capacity and optical basicity by reassessing different CaO-FetO-based slag systems. Mori’s correlation has been employed successfully in
KEZHUAN GU, NESLIHAN DOGAN, and KENNETH S. COLEY are with the Department of Materials Science and Engineering, McMaster Steel Research Centre, McMaster University, Hamilton, ON, L8S 4L7 Canada. Contact e-mail: [email protected] Manuscript submitted July 6, 2017.
METALLURGICAL AND MATERIALS TRANSACTIONS B
several studies[10–12] to determine phosphate capacity of slag. More recently, by reviewing the existing experimental data, Turkdogan[13] demonstrated that at low concentrations of P2O5 (up to 1 wt pct) the activity coefficient was independent of temperature, whilst it became temperature dependent when the content of P2O5 was greater than 10 wt pct. By studying phosphorus distribution between liquid iron and MgO-saturated CaO-FeOx slag, Suito et al.[14] proposed that the activity coefficient of P2O5 is temperature dependent for slags containing P2O5 concentrations less than 1 wt pct. Basu et al.[15,16] investigated phosphorus equilibrium between liquid steel and CaO-FetO-based slag with P2O5 ranged from 3 to 7 wt pct, and developed a correlation for prediction of P2O5 activity coefficient,[17] which considers the effect of temperature. A similar study was conducted by Assis et al.[18] for slag containing P2O5 between 1 and 3 wt pct. These workers did not show a correlation for temperature dependence of the P2O5 activity coefficient. More recently, after carrying out industrial experiments on dephosphorization of hot metal reacted with CaO-FetO-based slag containing 2 to 3 wt pct P2O5, Yang et al.[19] determined the activity coefficient of P2O5 using the ion and molecule coexistence theory. They further demonstrated that P2O5 activity coefficient can be reasonably predicted by any one of ten revised models collected from literature, which include the effects of chemical composition and temperature.
In a study of dephosphorization equilibria between liquid iron and highly basic CaO-based slags saturated with MgO, Ishii and Fruehan[10] investigated the effect of Al2O3 additions by correlating the phosphate capacity of the slags with the theoretical optical basicity, and showed that the results were represented reasonably by Mori’s correlation.[9] In a similar study to Ishii and Fruehan,[10] Li et al.[11] investigated the effect of Na2O and Al2O3
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