Thermodynamical calculations of vapor phase for Sb-S-O-H quarternary system

Abstract

The vapor phase equilibrium analysis has been carried out for the Sb-S-O-H quarternary system using a Constrained Chemical Potential Method (CCPM). A total 24 species in vapor phase and 9 condensable constituents have been considered. The resulting data for the system have been plotted on Gibbs triangles as a function of the gas phase composition. Decreasing the partial pressure of H2O, SO2 and SbS are likely to increase the fraction of Sb in the vapor phase and get a higher partial pressure of Sb4O6. The calculation results show that the vapor phase constituents in the Sb-S-O-H system are mainly composed of Sb4O6, SO2 and H2O. Under an appropriated temperature (1023K < T < 1073K), an oxygen partial pressure of 10−12.5 to 10−11.5 kPa and a sulfur partial pressure of less than 10−6.2 kPa, it is expected to result in a higher partial pressure of Sb4O6. The condensation of Sb2O3 (s) and S2 (s) is likely to occur in suitable oxygen partial pressure. The water vapor can accelerate the volatilization of Sb from Sb-bearing ores. XRD result of roast of Sb2S3 indicates that, in the water vapor atmosphere, the condensed product obtained is composed of Sb2O3 with small quantities of S2. It is in accordance with the calculation results (main Sb-bearing species is Sb4O6).