Phosphate Capacities of CaO–FeO–SiO2–Al2O3/Na2O/TiO2 Slags

Abstract

Abstract To effectively increase the dephosphorization efficiency of hot metals or the previous stage in the converter steelmaking process, phosphate capacities ( C P O 4 3 − ) {\rm{(}}{{\rm{C}}_{{\rm{PO}}_4^{3 - }}}) of CaO–FeO–SiO2–Al2O3/Na2O/TiO2 slags at 1300–1400°C were examined by laboratory experiments using equilibrating slag and pure solid iron foil. The data suggested that ( C P O 4 3 − ) {\rm{(}}{{\rm{C}}_{{\rm{PO}}_4^{3 - }}}) increases with decreasing temperature and increasing slag basicity. Compared to basicity, temperature considerably affected the phosphate capacities and tended to be the most important factor. The phosphate capacities of slag considerably decreased at a high temperature of 1400°C even under high binary basicity as well as high contents of Na2O and FeO. Moreover, with the increase in the content of FeO and Al2O3 in the slag, ( C P O 4 3 − ) {\rm{(}}{{\rm{C}}_{{\rm{PO}}_4^{3 - }}}) decreased. A low content of Na2O led to the increase in the phosphate capacities of slag, particularly at low temperatures of 1300–1350°C. The content of TiO2 in the slag considerably exhibited a weaker effect on ( C P O 4 3 − ) {\rm{(}}{{\rm{C}}_{{\rm{PO}}_4^{3 - }}}) . Furthermore, by regression analysis, ( C P O 4 3 − ) {\rm{(}}{{\rm{C}}_{{\rm{PO}}_4^{3 - }}}) was expressed as a function of the temperature and slag compositions as follows: logC PO 4 3 − = 0.041 ( % CaO ) − 0.086 log ( % FeO ) − 0.024 ( % SiO 2 ) − 0.02 ( % Al 2 O 3 ) + 0.067 ( % Na 2 O ) + 0.039 ( % TiO 2 ) + 56767 / T − 14.58 , ( R = 0.978 ) \eqalign{&{{\rm{log}}{{\rm{C}}_{{\rm PO}_4^{3 - }} = 0.041( \% {\rm CaO}) - 0.086{\rm log}({\rm{ \% }}{\rm FeO})} - 0.024( \% {\rm Si{O_2}})} \cr &{{ - 0.02({\rm{ \% }}{\rm A{l_2}{O_3})}} { + 0.067( \% {\rm N{a_2}O)} + 0.039( \% {\rm Ti{O_2})}}} \cr &+ 56767/{\rm T} - 14.58, ({\rm R} = 0.978)}}