Thermodynamic properties of WEEE-based minor elements in copper smelting processes

Research output: ThesisDoctoral ThesisCollection of Articles

Researchers

Research units

Abstract

Today, primary and secondary copper smelters are used as recycling facilities for different wastes, such as Waste Electric and Electronic Equipment (WEEE) -based copper scrap and industrial nonferrous waste. Consequently, multiple precious and rare metals, many of them not typical in primary concentrates, are entering the copper-making circuits with increasing concentrations. Thermodynamic properties of these WEEE-based minor elements are not known well enough or at all in copper smelting processes. In this study, the distribution equilibria of precious (Ag, Au, Pd and Pt) and high-tech (Ga, Ge, In and Sn) metals were investigated experimentally under primary and secondary copper smelting, as well as converting conditions. The experiments were executed employing a well-developed equilibration – quenching technique followed by direct phase analyses with electron microprobe (EPMA) and laser ablation inductively coupled plasma mass spectrometer (LA-ICP-MS). This study applied these experimental and analytical techniques to study minor element behaviour in copper/matte-slag systems for the first time. Especially, the use of the latter analytical technique was a great leap forward and enabled minor element concentration analyses even below 1 ppbw in metallurgical slags. The main thermodynamic parameter examined was the distribution coefficient, L = wt% of metal in matte or copper / wt% of metal in slag, which describes the behaviour of a minor element in smelting conditions. This research was implemented with a multi-disciplinary approach providing results for different fields of sciences and industries. The results present influences of different smelting conditions (especially pO2), primary saturation phase and slag composition on minor element equilibria. Moreover, the slag chemistry and copper losses in slags were examined. Precious metals – Au, Pd, Pt – were distributed and recovered efficiently in copper matte (L (m/s) > 10^2) and metal (L (Cu/s) > 10^4) in all conditions, much greater than previously considered in metallurgical literature. The results for high-tech metals Ga and Ge in the investigated copper-slag systems are novel and present the first data published in the literature. The distribution results for Ag, Sn and In were close to the distribution data found in literature. The thermodynamic data acquired is useful for industry in multiple purposes, such as process development, improving resource efficiencies and recoveries of the minor elements. To attain reliable simulation and modelling data of processes and metals behaviour, the presented properties need to be added into the thermodynamic databases of calculation programs.

Details

Original languageEnglish
QualificationDoctor's degree
Awarding Institution
Supervisors/Advisors
Publisher
  • Aalto University
Print ISBNs978-952-60-8605-7
Electronic ISBNs978-952-60-8606-4
Publication statusPublished - 2019
MoE publication typeG5 Doctoral dissertation (article)

    Research areas

  • precious metals, high-tech metals, black copper, distribution coefficient, recycling

ID: 37538513