Thermodynamic modelling of cupellation: activity of AgO 0·5 in molten PbO at 1000ºC

Abstract

The latest technology for processing Parkes silver crusts from lead refining uses vacuum induction furnace retorting to remove zinc, followed by bottom blown oxygen cupellation for oxidising lead to produce silver doré suitable for electrorefining. A computational thermodynamics model of the cupellation process has been developed to predict the effect of operating variables on the final doré composition and silver recovery to doré, as an aid in optimising the silver production process. However, this model was limited by the absence of any thermodynamic data on AgO_0·5 in solution in molten PbO. In the present work, the activity of AgO_0·5 in molten PbO has been determined at 1000ºC over the composition range of interest. It was found that the activity of AgO_0·5 obeys Henry's law and that the limiting activity coefficient is 0·65. These data are used in the computational thermodynamics model to discuss some important relationships in bottom blown oxygen cupellation.

Keywords

CUPELLATION SILVER LEAD MODELLING THERMODYNAMIC MODELLING REFINING

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