Thermodynamic Analysis of V-concentrating Phase Formation in V-bearing Steelmaking Slag Modified by MgO

Abstract

In the study, magnesium oxide acting as modifier was added to V-bearing steelmaking slag to concentrate vanadium, and then the effect of magnesium oxide on the formation of V-concentrating phase during cooling was investigated. Experimental results show that, in the case of the original slag, di-calcium silicate along with most of vanadate and phosphate in the slag forms solid solution, calcium ferrite which contains small part of vanadium in the slag and matrix without vanadium in turn precipitate during slowly cooling; For the sample with 8% MgO addition, two new phases (merwinite and V-concentrating phase) generate during slowly cooling, and the amount of di-calcium silicate decreases. Merwinite phase doesn’t contain vanadium, and V-concentrating phase (Ca₃(V,P)₂O₈·nCa₂SiO₄) contains 17–19% V₂O₅ by mass; For the sample with 16% MgO addition, another new phase (monticellite) precipitates from liquid slag, the phase of di-calcium silicate disappears, and most of vanadium concentrates in V-concentrating phase-Ca₃(V,P)₂O₈·nCa₂SiO₄ (18–21%V₂O₅).