Experimental Determination of the Phase Equilibrium in the Cu-O-ZnO-SiO2-CaO-MgO System
School of Chemical Technology | Doctoral thesis (article-based) | Defence date: 2016-11-27
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Aalto University publication series DOCTORAL DISSERTATIONS, 243/2016
AbstractDue to the intensive consumption of high quality concentrates, copper smelters are increasing portions of multi-mineral ores and secondary scraps in their feeding materials. The smelting of complex materials is always accompanied by the formation of large amount of slag. Impurities in the feeding materials will be oxidized during the smelting process, and those oxides will form the slag phase together with fluxes. Certain amount of refractory materials will be eroded by molten phases, and then merge into the slag phase. The monitoring of slag compositions and properties has significant importance. Zinc is one of the major impurity elements in copper making, and it will be oxidized to zinc oxide (ZnO) in the smelting process. Zinc content in copper scraps, for example WEEE materials and waste brass, is also quite high, and it will also be oxidized and merge into the slag phase. Currently, ZnO content in copper smelting slags is increasing. However, the thermodynamic information about high ZnO content slag is still incomplete. The thermodynamic properties of the slag can be achieved by software calculation. But there are a lot of uncertainties in applying those extrapolated information into practice. Accurate experimental data are needed in the thermodynamic assessment of those less known systems.With the guidance of calculated phase diagrams by MTDATA 5.10 and its Mtox 8.1 database, the equilibration/quenching/SEM/EDS+EPMA technique has been successfully applied in investigating the phase relationship in the Cu-O-ZnO-SiO2-CaO-MgO system and its subsystems. Phase relationships in a wide temperature range (1000 °C – 1700 °C), and at various oxygen partial pressures (pO2 = 0.21 atm, pO2 = 0.01 atm, and in pure argon) have been systematically studied. Liquidus compositions and eutectic points in the ZnO-SiO2, ZnO-CaO, Cu-O-ZnO, Cu-O-SiO2, Cu-O-ZnO-SiO2, Cu-O-ZnO-CaO, and Cu-O-ZnO-MgO systems have been investigated. Sub-solidus lines in the ZnO-CaO, ZnO-MgO binaries have also been determined. The solubility behavior of copper oxide in the other terminal phases have been carefully checked as well. The best fitted phase diagrams have been compared with the resultsfrom the literature, and with the calculated phase diagrams from MTDATA 5.10 software and Mtox 8.1 database, and the differences are significant. The thermodynamic descriptions of those systems in the database should be updated, and the Cu-O-ZnO-SiO2-CaO-MgO system and its sub-systems need re-assessments. This study provides novel data for both scientific research and industrial practices.
Supervising professorLiu, Zhihong, Prof., Central South University, P. R. China
Taskinen, Pekka, Prof., Aalto University, Department of Materials Science and Engineering, Finland
Thesis advisorTaskinen, Pekka, Prof., Aalto University, Department of Materials Science and Engineering, Finland
liquidus, solidus, sub-solidus, phase diagram, thermodynamic, smelting, slag, pyrometallurgy
[Publication 1]: Xia, Longgong; Liu, Zhihong; Taskinen, Pekka Antero. 2015. Experimental determination of the liquidus temperatures of the binary (SiO2-ZnO) system in equilibrium with air. Elsevier. Journal of the European Ceramic Society, volume 35, issue 14, pages 4005-4010. ISSN: 0955-2219.
DOI: 10.1016/j.jeurceramsoc.2015.07.007 View at publisher
[Publication 2]: Xia, Longgong; Liu, Zhihong; Taskinen, Pekka. 2016. Phase equilibrium study of the CaO-ZnO system. Wiley. Journal of the American Ceramic Society, volume 99, issue 11, pages 3809-3815. ISSN: 0002-7820.
DOI: 10.1111/jace.14405 View at publisher
[Publication 3]: Xia, Longgong; Liu, Zhihong; Taskinen, Pekka. 2016. Solubility study of the halite and wurtzite solid solutions in the MgO-ZnO system within temperature range from 1000 to 1600 °C. Elsevier. Journal of Alloys and Compounds, volume 687, issue 5, pages 827-832. ISSN: 0925-8388.
DOI: 10.1016/j.jallcom.2016.06.191 View at publisher
[Publication 4]: Xia, Longgong; Liu, Zhihong; Taskinen, Pekka Antero. 2016. Phase equilibria study of Cu-O-ZnO system in various oxygen partial pressures. Elsevier. Ceramics International, volume 42, issue 4, pages 5418-5426. ISSN: 0272-8842.
DOI: 10.1016/j.ceramint.2015.12.082 View at publisher
[Publication 5]: Xia, Longgong; Liu, Zhihong; Taskinen, Pekka Antero. 2016. Equilibrium study of the Cu-O-SiO2 system at various oxygen partial pressures. Elsevier. Journal of Chemical Thermodynamics, volume 98, pages 126-134. ISSN: 0021-9614.
DOI: 10.1016/j.jct.2016.03.023 View at publisher
[Publication 6]: Xia, Longgong; Liu, Zhihong; Taskinen, Pekka Antero. 2016. Experimental Determination of the Liquidus Surface of the Cu-O-CaO-ZnO system in equilibrium with air. Springer. Metallurgical and Materials Transaction B, volume47, issue 6. ISSN: 1073-5615.
DOI: 10.1007/s11663-016-0800-0 View at publisher
- [Publication 7]: Xia, Longgong; Liu, Zhihong; Taskinen, Pekka Antero. 2016. Experimental determination of the liquidus surface of the Cu-O-MgO-ZnO system in equilibrium with air, Copper 2016. Kobe, Japan, November. (Accepted, paper ID7283)
[Publication 8]: Xia, Longgong; Liu, Zhihong; Taskinen, Pekka. 2016. Experimental determination of the liquid phase domain of the Cu-O-ZnO-SiO2 system in equilibrium with air. Taylor & Francis Group. Canadian Metallurgical Quarterly. ISSN: 0008-4433.
DOI: 10.1080/00084433.2016.1245944 View at publisher