Implementation of flame optical emission spectroscopy system for converter Fe end-point control associated with Ni-Cu-S-PGM converter mattes

Abstract

Iron endpoint control in nickel-copper converting operations is critical for optimal operation of subsequent hydrometallurgical extraction and refining operations and has additional impacts where such operations are also associated with platinum group metal (PGM) processing. The identification of the optimal converter iron endpoint, its impact on operations and real time inferential detection are discussed. An evaluation of the thermochemistry was conducted with thermodynamic equilibrium modelling software and validation of the data was performed with actual plant data and operating experience. The impact of iron endpoint on the quality of the matte, from a downstream refining perspective, environmental and safety considerations and the impact on smelter costs were qualitatively evaluated. Different methodologies of end-point control in the converter are discussed with emphasis on flame optical emission spectroscopy as the preferred endpoint monitoring method. While optical emission spectroscopy as a tool to determine the oxidation state in a converter is well established in the Cu industry its application in Ni matte converting is recent. Western Platinum has been the first PGM producer to apply this technology for iron endpoint control. Results achieved after implementation are presented and the current focus/development areas are listed, specifically around the practice in which the converters at Western Platinum Limited finishes the blow before granulation.