Phase Equilibria Studies of Zinc-containing Copper Smelting Slags Hongquan Liu Master of Engineering A thesis submitted for the degree of Doctor of Philosophy at The University of Queensland in 2016 School of Chemical Engineering Abstract The smooth operation and productivity of the copper smelters are highly dependent on the comprehension of slag chemistry under the smelting conditions. Phase equilibria of slag principally control the melting temperatures of the slags and proportions of solids at fixed operating temperatures. Due to the decrease of copper ore grade as well as the use of complex feeds, appreciable amount of ZnO is present in the copper smelting slags. The aim of the present study is to investigate the liquid temperature and phase relations of the zinc- containing copper smelting slag systems. Due to the fast vaporization of zinc under reducing conditions, experimental techniques have been developed to enable the phase equilibrium studies of zinc-containing system at copper smelting conditions to be carried out. The experimental procedures in present studies involve master slags preparation, high temperature equilibration, quenching and electron probe X-ray microanalysis (EPMA). The methodology applied in the present study allows the phase assemblages and compositions of the phases existing in the quenched samples to be spontaneously analysed by EPMA. The phase equilibria studies on the zinc-containing slag systems have been conducted -8 under fixed oxygen partial pressure (Po2) at 10 atm at temperature range from 1443 K (1170 °C) to 1573 K (1300 °C). The slag systems investigated in the present studies including: (1) A reinvestigation on “FeO”-SiO2 system at temperature range from 1473 K (1200 °C) to 1573 K (1300 °C). The experimental outcomes improve the accuracy of phase -8 diagram of this system at Po2 10 atm. (2) ZnO-“FeO”-SiO2 system at temperature range from 1443 K (1170 °C) to 1573 K (1300 °C). The experimental outcomes indicate that the liquidus temperature is much higher than “FeO”-SiO2 pseudo-binary system with the presence of ZnO in the slag. (3) ZnO-“FeO”-SiO2-Al2O3 system at temperatures, 1523 K (1250 °C), 1543 K (1270 °C) and 1573 K (1300 °C) with Al2O3 varying from 2 to 6 wt pct. The experimental results show that the increase of Al2O3 content in the slag phase increases the liquidus temperature in the spinel phase. The distribution of ZnO with the presence of Al2O3 tends to be in spinel than the liquid phase. (4) ZnO-“FeO”-SiO2-MgO system at temperatures, 1523 K (1250 °C), 1543 K (1270 °C) and 1573 K (1300 °C) with MgO varying from 2 to 6 wt pct. The experimental results indicate that increasing MgO content in the slag phase significantly increases the liquidus temperature in the spinel primary phase field. The presence of MgO in the ZnO-“FeO”-SiO2-MgO system has minor effect on partitioning behaviour of ZnO between in the spinel and liquid phases. (5) ZnO-“FeO”-SiO2-CaO system at temperatures, 1523 K (1250 °C), 1543 K (1270 °C) and 1573 K (1300 °C) with CaO varying from 2 to 6 wt pct and 2 wt pct sulphur. The experimental outcomes suggest that the increasing of CaO concentration in the slag phase will significantly increases the liquidus temperature in the spinel primary phase field; the introduction of CaO into the slag has minor effect on the ZnO partitioning behaviour between the spinel and liquid phases. (6) Preliminary experimental work ZnO-“FeO”-SiO2-CaO-S system at temperatures 1443 K (1170 °C) and 1473 K (1200 °C). The experiment results indicate that 2 wt pct of sulphur in the liquid phase significantly decrease the liquidus temperature, up to 70 K compared to the ZnO-“FeO”-SiO2-CaO system. The experimental work from present studies fill the gap of zinc-containing copper smelting slag under conditions relevant to that in industrial practice. With the experimental outcomes obtained in present studies, more accurate information of the slag chemistry of zinc-bearing slag systems are now available for industrial smelter operation as well as for the thermodynamic modelling of the copper smelting slags. The evaluation of minor elements (arsenic and zinc) distributions among the gas / slag / matte phases during the copper smelting process were carried out. Literature reviews of existing experimental data and models of the distributions show that the operating parameters in smelting process have major impact on the fractional distribution behaviours of As and Zn. Thermodynamic calculation software - FactSage 6.4 was applied to predict the distribution behaviours of As and Zn as function of the operating parameters during the smelting process and compared with the literatures. The study of minor element distributions will improve the understanding of thermodynamic behaviours, and benefit the management of minor elements during copper smelting process. Declaration by author This thesis is composed of my original work, and contains no material previously published or written by another person except where due reference has been made in the text. I have clearly stated the contribution by others to jointly-authored works that I have included in my thesis. I have clearly stated the contribution of others to my thesis as a whole, including statistical assistance, survey design, data analysis, significant technical procedures, professional editorial advice, and any other original research work used or reported in my thesis. The content of my thesis is the result of work I have carried out since the commencement of my research higher degree candidature and does not include a substantial part of work that has been submitted to qualify for the award of any other degree or diploma in any university or other tertiary institution. I have clearly stated which parts of my thesis, if any, have been submitted to qualify for another award. I acknowledge that an electronic copy of my thesis must be lodged with the University Library and, subject to the policy and procedures of The University of Queensland, the thesis be made available for research and study in accordance with the Copyright Act 1968. I acknowledge that copyright of all material contained in my thesis resides with the copyright holder(s) of that material. Where appropriate I have obtained copyright permission from the copyright holder to reproduce material in this thesis. Publications during candidature 1. H. Liu, Cui Z., Chen M. and Zhao B., “Phase equilibrium study of ZnO-“FeO”-SiO2 system -8 at fixed Po2 10 atm”, Proceedings of High Temperature Processing Symposium, Editors M. Akbar Rhamdhani and Geoffrey Brooks, publisher Swinburne University of Technology, Melbourne, Australia, ISBN 978-0-9875930-2-3, 2014, pp. 117-124. 2. H. Liu, Z. Cui, M. Chen and B. Zhao, “Phase Equilibrium Study of ZnO-"FeO"-SiO2 -8 System at Fixed Po2 10 atm”, Metall. Mater. Trans. B, 47 (2016): 164-173. 3. Liu H., Cui Z., Chen M. and Zhao B., “Phase equilibria studies in the system ZnO-“FeO”- SiO2-Al2O3 for copper smelting slags”, Proceedings of High Temperature Processing Symposium, Editors Geoffrey Brooks and M. Akbar Rhamdhani, publisher Swinburne University of Technology, Melbourne, Australia, ISBN 978-0-9875930-3-0, 2015, pp. 99- 102. 4. H. Liu, Z. Cui, M. Chen and B. Zhao, “Phase Equilibria Study of the ZnO-"FeO"-SiO2- -8 Al2O3 System at Po2 10 atm”, Metall. Mater. Trans. B, 47 (2016): 1113-1123. Publications included in this thesis H. Liu, Z. Cui, M. Chen and B. Zhao, “Phase Equilibrium Study of ZnO-"FeO"-SiO2 System -8 at Fixed Po2 10 atm”, Metall. Mater. Trans. B, 47 (2016): 164-173. – incorporated as Chapter 5. Contributor Statement of contribution H. Liu Designed experiments (60%) Wrote the paper (60%) Z. Cui Provided industrial smelting operating data and samples M. Chen Designed experiments (10%) Wrote the paper (15%) B. Zhao Designed experiments (30%) Wrote the paper (25%) H. Liu, Z. Cui, M. Chen and B. Zhao, “Phase Equilibrium Study of ZnO-"FeO"-SiO2-Al2O3 -8 System at Fixed Po2 10 atm”, Metall. Mater. Trans. B, 47 (2016): 1113-1123 – incorporated as Chapter 6. Contributor Statement of contribution H. Liu Designed experiments (65%) Wrote the paper (80%) Z. Cui Provided industrial smelting operating data M. Chen Designed experiments (15%) Wrote the paper (5%) B. Zhao Designed experiments (20%) Wrote the paper (15%) Contributions by others to the thesis Contributions by Prof. Baojun Zhao and Dr. Mao Chen in experiment design, concept, analysis, interpretation, drafting, and writing in the advisory capacity. Statement of parts of the thesis submitted to qualify for the award of another degree None Acknowledgements I would like to thank my principle supervisor Prof. Baojun Zhao for his support and guidance all through the candidature. I also wish to thanks my associate supervisor Prof. Anh V. Nguyen for his valuable suggestions and encourage. I also would like to thank the following for their assistance during my study: Dr. Mao Chen at the University of Queensland who helped me in experiments design, outcomes interpretation and paper writing. Ms. Jie Yu at the University of Queensland who helped me developing the high temperature experimental skills. Ms. Ying Yu, Mr Ron Rasch and Dr. Kim Sewell from the Centre for Microscopy and Microanalysis (CMM) within the University of Queensland who trained and assisted me using the equipment at CMM. I wish to thank Dongying Fangyuan Nonferrous Metals Co., Ltd. and The University of Queensland for their financial support of this research through “Fangyuan Fellowship” program, and to the University of Queensland International Research Tuition Award (UQIRTA) and China Scholarship Council (CSC) for providing scholarships for Hongquan Liu. Finally, I would like to thank my parents and beloved wife Min Gao for the supporting and encourage, especially at the tough time during the candidature.