Activities of Components in Iron oxysulphide Melt in Equilibrium with Solid Iron

Abstract

Equilibrium between H₂-H₂O-H₂S mixtures and iron oxysulphide melts in coexistence of solid iron was accomplished by means of the gas circulating method. The temperature range of measurements was 1 000 to 1 200°C, and the mole fractions of oxygen and sulphur in the melt were N_o =00.35 and N_s= 0.180.43, respectively. The oxygen pressure in gas was measured by oxygen galvanic cell using calcia-stabilized zirconia as a solid electrolyte. The sulphur pressure in gas was determined by chemical analysis.
The activities of oxygen and sulphur in the melt showed slightly positive deviation from the fractional concentration of each anion i, N'_i =N_i/(N_o+N_s) modified by a solution model.
The partial molar quantities of species in the solution at 1 100°C were calculated from results of the activities. It was shown that oxygen exothermically dissolves into the solution and has a small inclination of imperfect mixing at N'_o=0.2, whereas sulphur plays nearly an ideal behavior in the solution.
The sulphur potential in equilibrium with iron, wustite and the melt was in close agreement with those in earlier works.