Experimental study of phase equilibria in the PbO-ZnO-“Fe2O3”-CaO-SiO2 system in air for high lead smelting slags (CaO/SiO2=0.35 and PbO/(CaO + SiO2)=5.0 by weight)

Experimental studies on phase equilibria in the multicomponent system PbO-ZnO-CaO-SiO₂-FeO-Fe₂O₃ in air have been conducted to characterize the phase relations of a complex slag system used in commercial lead oxidation smelting. The liquidus in the pseudo-ternary section ZnO-“Fe₂O₃”-(PbO + CaO + SiO₂) with the CaO/SiO₂ weight ratio of 0.35 and the PbO/(CaO + SiO₂) weight ratio of 5.0 has been constructed using results of over 100 high-temperature equilibration and quenching experiments followed by electron probe X-ray microanalysis. The liquidus in this pseudoternary section contains primary phase fields of spinel (zinc ferrite) Zn _x Fe_3−x O_4+y , zincite Zn _u Fe_1−u O, melilite Pb _v Ca_2−v Zn _w Fe_1−w Si₂O₇, hematite Fe₂O₃, magneto-plumbite PbFe₁₀O₁₆, and dicalcium silicate Ca_2−t Pb _t SiO₄. The laboratory results are compared with the slags obtained from an industrial reactor.