Electron beam and Mössbauer techniques combined to optimise base metal partitioning in the furnace

Abstract.

Furnace slag and matte samples from Anglo Platinum smelters were analysed using a combination of electron microbeam and Mössbauer techniques. The object of the investigation was to establish the distribution of the base metals (nickel, copper and cobalt) in slag, and to predict their recovery by milling and flotation. In addition, the data was used to assess the viability of process optimisation using a modelling program. Slag samples were analysed quantitatively by EPMA, employing longer counting times for trace elements, and correcting for Fe-K_β peak interference on Co-K_α An automated software program was used to run phase specific analysis of entrained matte inclusions in slag. The technique allows simultaneous measurement of inclusion size, and correlation of size with composition. The results were combined with EPMA data to determine maximum theoretical base metal recovery from slag.

Partitioning behaviour of elements between slag and matte depends on many parameters such as temperature, slag and matte composition, and oxygen partial pressure (pO₂). Initially, predicted base metal distributions as calculated using the FactSage modelling program did not agree well with measured levels. Later, the use of Mössbauer Fe³⁺/Fe²⁺ ratios, which defined pO₂ as more oxidising than previously assumed, and entrained matte composition results, allowed more accurate predictions to be made.