Viscosity Studies of High-Temperature Metallurgical Slags Relevant to Ironmaking Process

Slags are molten oxides presenting in a number of high-temperature processes. In ironmaking process, the metallurgical properties of blast furnace slags are determined largely by its viscosity. Understanding and controlling the behavior of the slag phase is crucial in improving the operational and economical efficiencies. However, high-temperature viscosity measurement is practically difficult, timeand cost-consuming. There is a necessity to develop a reliable mathematical model for the viscosity prediction through the review of experimental data and fundamental theory. As foundation work, abundant viscosity measurements and models have been examined and evaluated, including over 3000 viscosity data in the CaO-MgO-Al2O3-SiO2 system and 16 viscosity models. Over the past 10 years, there has been increasing attentions on wide composition range of slag viscosity due to the continuous consumption of complex iron ores. In addition, the impacts of eight minor elements (including F, Ti, B, Fe, Mn, Na, K, and S) on slag viscosity have been studied for practical purpose. Slag viscosity is determined by its structure, which is the theoretical base of the mathematical model. The structures of the quenched silicate slags were quantitatively investigated utilizing Raman spectroscopy. It is accepted that the application of Raman spectroscopy can disclosure the vibration units of molten slag, which can be interpreted the structural of silicate melts (amorphous glass phase). In the blast furnace operations, some solid phases such as oxide precipitates, coke or Ti(CN) can be present in the slag. In addition, the precipitation of solid particles was commonly observed in iron, steel, copper and other pyrometallurgy process. These solids can significantly increase the viscosity of the slag causing operating difficulty. There is a research gap that the solid impact on suspension was limited investigated under high-temperature condition due to uncertainty. Referring to the research gap of viscosity study of blast furnace slag, the following goals have been achieved by the Ph.D. candidate: 1. Review and evaluated the experimental methodologies, viscosity data, and models relevant to the blast furnace slag in CaO-MgO-Al2O3-SiO2 system (Chapter 2) 2. Based on the collected data and models, an accurate viscosity model has been developed to predict the viscosity of blast furnace slag in CaO-MgO-Al2O3-SiO2 system (Chapter 45) 3. Research on the viscosity impact of minor elements on the blast furnace final slag in CaOMgO-Al2O3-SiO2 based system. (Chapter 4-5) 4. Quantitative investigation of the microstructural units of silicate slag utilizing Raman spectroscopy. (Chapter 6) 5. Investigation of the solid phase impact on the viscosity of liquid slag. (Chapter 7) 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, and 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 General Award Rules of The University of Queensland, immediately 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. Chen. Han, Mao. Chen, Weidong Zhang, Zhixing Zhao, Tim Evans, Anh V. Nguyen and Baojun. Zhao * , “Viscosity Model for Iron Blast Furnace Slags in SiO2-Al2O3-CaO-MgO system”, Steel Research International, 2015, vol.85 (6), pp. 678-685 2. Chen. Han, Mao. Chen, Weidong. Zhang, Zhixing. Zhao, Tim. Evans and Baojun. Zhao * , “Evaluation of Existing Viscosity Data and Models and Developments of New Viscosity Model for Fully Liquid Slag in the SiO2-Al2O3-CaO-MgO System”, Metallurgical and Material Transactions B, 2016, Vol 47 (5), pp. 2861-2874 3. Chen. Han, Mao. Chen, Ron. Rasch, Ying. Yu and Baojun. Zhao * , “Structure Studies of Silicate Glasses by Raman Spectroscopy”, Advances in Molten Slags, Fluxes, and Salts: Proceedings of The 10 th International Conference on Molten Slags, Fluxes and Salts, Seattle, United States, 2016, pp. 175-182 4. Chen. Han, Mao. Chen, Weidong. Zhang, Zhixing Zhao, Tim. Evans and Baojun. Zhao, “Viscosity Model for Blast Furnace Slags Including Minor Elements”, The 10 th CSM Steel Congress & The 6 th Baosteel Biennial Academic Conference 2015, Shanghai, China, 2015, pp. 95-103 5. Chen. Han, Mao. Chen, Weidong. Zhang, Zhixing Zhao, Tim. Evans, Anh V. Nguyen and Baojun. Zhao * , “Development of viscosity model for SiO2-CaO-MgO-Al2O3-“FeO” slags in ironmaking process”, High Temperature Processing Symposium, 2015, Melbourne, Australia, pp. 103-106 Publications included in this thesis 1. Chen. Han, Mao. Chen, Weidong Zhang, Zhixing Zhao, Tim Evans, Anh V. Nguyen and Baojun. Zhao * , “Viscosity Model for Iron Blast Furnace Slags in SiO2-Al2O3-CaO-MgO system”, Steel Research International, 2015, vol.85 (6), pp. 678-685 – incorporated as Chapter 4.1 Contributor Statement of contribution Chen Han (Candidate) Wrote the paper (100%) Baojun Zhao* Discussed and edited paper (45%) Mao Chen Discussed and edited paper (45%) Tim Evans Discussed and edited paper (5%) Anh V Nguyen Discussed and edited paper (5%) Weidong Zhang Provided industrial advices (50%) Zhixing Zhao Provided industrial advices (50%) 2. Chen. Han, Mao. Chen, Weidong. Zhang, Zhixing. Zhao, Tim. Evans and Baojun. Zhao * , “Evaluation of Existing Viscosity Data and Models and Developments of New Viscosity Model for Fully Liquid Slag in the SiO2-Al2O3-CaO-MgO System”, Metallurgical and Material Transactions B, 2016, Vol 47 (5), pp. 2861-2874 – incorporated as Chapter 4.2 Contributor Statement of contribution Chen Han (Candidate) Wrote the paper (100%) Baojun Zhao* Discussed and edited paper (45%) Mao Chen Discussed and edited paper (45%) Tim Evans Discussed and edited paper (5%) Anh V Nguyen Discussed and edited paper (5%) Weidong Zhang Provided industrial advices (50%) Zhixing Zhao Provided industrial advices (50%) 3. Chen. Han, Mao. Chen, Ron. Rasch, Ying. Yu and Baojun. Zhao * , “Structure Studies of Silicate Glasses by Raman Spectroscopy”, Advances in Molten Slags, Fluxes, and Salts: Proceedings of The 10 th International Conference on Molten Slags, Fluxes and Salts, Seattle, United States, 2016, pp. 175-182 – incorporated as Chapter 6 Contributor Statement of contribution Chen Han (Candidate) Wrote the paper (100%) Baojun Zhao* Discussed and edited paper (45%) Mao Chen Discussed and edited paper (45%) Ron Rasch Assisted in the Raman spectra analysis (50%) Ying Yu Assisted in the Raman spectra analysis (50%) 4. Chen. Han, Mao. Chen, Weidong. Zhang, Zhixing Zhao, Tim. Evans and Baojun. Zhao, “Viscosity Model for Blast Furnace Slags Including Minor Elements”, The 10 th CSM Steel Congress & The 6 th Baosteel Biennial Academic Conference 2015, Shanghai, China, 2015, pp. 95-103 – incorporated as Chapter 4.2; Contributor Statement of contribution Chen Han (Candidate) Wrote the paper (100%) Baojun Zhao* Discussed and edited paper (45%) Mao Chen Discussed and edited paper (45%) Tim Evans Discussed and edited paper (5%) Anh V Nguyen Discussed and edited paper (5%) Weidong Zhang Provided industrial advices (50%) Zhixing Zhao Provided industrial advices (50%) 5. Chen. Han, Mao. Chen, Weidong. Zhang, Zhixing Zhao, Tim. Evans, Anh V. Nguyen and Baojun. Zhao * , “Development of viscosity model for SiO2-CaO-MgO-Al2O3-“FeO” slags in ironmaking process”, High Temperature Processing Symposium, 2015, Melbourne, Australia, pp. 103-106 – incorporated as Chapter 5.2 Contributor Statement of contribution Chen Han (Candidate) Wrote the paper (100%) Baojun Zhao* Discussed and edited paper (45%) Mao Chen Discussed and edited paper (45%) Tim Evans Discussed and edited paper (5%) Anh V Nguyen Discussed and edited paper (5%) Weidong Zhang Provided industrial advices (50%) Zhixing Zhao Provided industrial advices (50%) Contributions by others to the thesis Contributions by Professor Baojun Zhao 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 express my sincere gratitude to my advisor team Prof. Baojun Zhao (principal), Prof Anh Nguyen and Dr. Tim.Evans for their guidance and support the research projects and this thesis completion I would like to acknowledge the Beijing Shougang Co., Ltd, China and Rio Tinto Iron Ore, Australia for financial support. I thank to Dr. Mao Chen for fruitful discussions and assistance in preparing this thesis. I am very grateful to the lab assistant Ms, Jie Yu, for her help and support on the completion of experimental work.