The high temperature thermodynamics of the Ni-Co-S and Fe-Co-S ternary systems

grantor: University of TorontoThe metal saturation line and tie-lines in the nickel-cobalt-sulphur ternary system have been determined between 1273 and 1573 K. Those for the iron-cobalt-sulphur ternary system have also been determined between 1473 and 1623 K. The experiments were conducted by equilibrating the liquid sulphide phase with the metallic alloy phase. The liquid sulphide phase was sampled and chemically analyzed. The alloy phase was analyzed by an electron microprobe. It was found that the metal saturation line data available in the literature for the iron-cobalt-sulphur system were very different from the results of this study. To measure the partial pressure of sulphur in these two ternary systems, a gas equilibrium technique was used. A gas mixture of H2S/H 2 was used to fix the partial pressure of sulphur. The partial pressures of sulphur in the nickel-cobalt-sulphur ternary system were measured at 1373, 1473 and 1573 K, while in the iron-cobalt sulphur system, they were measured at 1473, 1548 and 1623 K. The attainment of equilibrium was evaluated by several techniques. The iso-activity contours for Ni, Fe, and Co were determined by application of the Gibbs Duhem equation using Schuhmann's method for ternary systems. The cobalt activity coefficients in dilute solutions of cobalt in the nickel-cobalt-sulphur system were determined. It was found that these systems had a negative deviation from Raoult's law and up to about 0.02 mole fraction of cobalt the activity coefficient of cobalt was constant. The cobalt activities in the iron-cobalt-sulphur ternary system were also determined. At 1548 and 1623 K, cobalt behaved in an ideal manner up to approximately 0.02 mole fraction, above which it exhibited a positive deviation from ideality. At 1473 K, up to approximately 0.05 mole fraction, the activity coefficient of cobalt was constant. From the experimental data, the partial heats of solution for nickel, iron, cobalt, and sulphur were calculated. The integral heats of solution for the Ni-Co-S and the Fe-Co-S ternary systems were determined.Ph.D