THERMODYNAMICS AND PHASE-RELATIONS OF THE FE-O-S-SIO(2)(SAT) SYSTEM AT 1200-DEGREES-C AND THE EFFECT OF COPPER

A laboratory investigation was carried out in which iron was reacted in silica crucibles with an atmosphere of controlled oxygen and sulfur partial pressures. The equilibrium compositions of the melts were determined over the range 10(-12) to 10(-9) atm oxygen and 10(-2.75) to 10(-1) atm sulfur and it was found that the Fe-O-S-SiO2 system can exist as either a slag or oxysulfide. The oxysulfide contained appreciable quantities of dissolved oxygen and silica, although the levels decreased as the sulfur content was increased. Sulfur also had the effect of reducing the solubility of silica in the slag. When copper was added to the system, the solubility of oxygen and silica in the oxysulfide phase decreased dramatically. The results are examined in terms of the thermodynamics of the relevant reactions, and the predominance area diagram for the copper-free system was established by combining the present results with those of earlier investigations.