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Fundamental Study of Red Mud Based Fluxes for Desulphurization and Dephosphorization of Hot Metal

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Fundamental Study of Red Mud Based Fluxes for Desulphurization and Dephosphorization of Hot Metal FUNDAMENTAL STUDY OF RED MUD BASED FLUXES FOR DESULPHURIZATION AND DEPHOSPHORIZATION OF HOT METAL by Abdolkarim Danaei B.Sc. Isfahan University of Technology, Iran, 1985 M.Sc. Sharif University of Technology, Iran, 1993 A dissertation presented to Ryerson University in partial fulfillment of the requirements for the degree of Doctor of Philosophy in the Program of Mechanical and Industrial Engineering Toronto, Ontario, Canada, 2015 © Abdolkarim Danaei, 2015 AUTHOR’S DECLARATION FOR SUBMISSION OF ELECTRONIC DISSERTATION I hereby declare that I am the sole author of this dissertation. This is a true copy of the dissertation, including any required final revisions, as accepted by my examiners. I authorize Ryerson University to lend this dissertation to other institutions or individuals for the purpose of scholarly research. I further authorize Ryerson University to reproduce this dissertation by photocopying or by other means, in total or in part, at the request of other institutions or individuals for the purpose of scholarly research. I understand that my dissertation may be made electronically available to the public. ii Abstract FUNDAMENTAL STUDY OF RED MUD BASED FLUXES FOR DESULPHURIZATION AND DEPHOSPHORIZATION OF HOT METAL Doctor of Philosophy, 2015 Abdolkarim Danaei B.Sc. Isfahan University of Technology, Iran M.Sc. Sharif University of Technology, Iran Mechanical and Industrial Engineering Ryerson University Bauxite residue, also known as red mud, is generated during alumina production and is an abundant industrial waste material. Continuously increasing environmental concerns, together with scarcity of traditional mineral resources, have created a thrust to re-use the material. Red mud contains significant amounts of iron oxide and sodium hydroxide, hence a highly basic (pH > 10) slurry. In this research, the use of red mud as starting material for preparation of iron refining fluxes was evaluated. Red mud based fluxes and hot metal were equilibrated in graphite crucibles at the temperature range of 1300 ºC to 1400 °C and oxygen partial pressures range of 10-2 atm to 10-6 atm. It was found that the sulphide capacity increases with lime addition to a maximum 32 wt% CaO and decreases with increasing Al2O3, TiO2 and SiO2 content in the fluxes saturated with lime. An iron foil equilibrium technique was employed to obtain precise measurements of phosphorus distribution between carbon saturated iron and red mud based fluxes. The measurements indicate iii that the equilibrium phosphorus distribution ratio initially increases with rise in FeO or CaO concentration of the fluxes and then drops. The melting behavior of the fluxes was also studied by visualizing the deformation of flux pellets as they were heated using a high temperature microscopy technique. Measurements of characteristic temperature for different fluxes indicated the melting property is a function of slag basicity. Therefore, optical basicity was used to establish a correlation between basicity of the red mud based fluxes and their melting properties. iv Acknowledgements First, and most of all, I would like to thank my supervisor Professor Ravi Ravindran whose untiring support and seemingly unlimited belief in me made this research work possible. I would also like to thank my co-supervisors Professors Alexander McLean and Mansoor Barati, for their excellent guidance, valuable discussion in analyzing the results and financial support during my graduate study. I take this opportunity to thank Dr. Y. D. Yang for helping me to start the work and C-S analysis. I am also grateful to Dr. H. Soda for valuable advice during this project. I would like to extend my thanks to Mr. Alan Machin and Dr. Sophie Lun Sin for their kind help and support during this work. I am indebted to George Kretschmann of Geology Dep. for XRD and Process Research ORTECH (PRO) for their assistance and support in XRF analyses. I would like to offer my respects to my colleagues who supported me during the project in Near- net-shape Processing of Materials (CNPM) group at Ryerson University and Sustainable Materials Processing Research (SMPR) group at the University of Toronto. Lastly, I owe my deepest gratitude to my wife, son and daughter whose unhesitating support during my project enabled me to continue working with peace of mind. Abdolkarim Danaei v Dedication To my wife, son and daughter vi Table of Contents Author’s Declaration .................................................................................................................................... ii Abstract ........................................................................................................................................................ iii Acknowledgements ....................................................................................................................................... v Dedication .................................................................................................................................................... vi Table of Contents ........................................................................................................................................ vii List of Tables ............................................................................................................................................... xi List of Figures ............................................................................................................................................. xii List of Appendices ..................................................................................................................................... xvi Nomenclature ............................................................................................................................................ xvii Acronyms ................................................................................................................................................... xix Chapter 1 ....................................................................................................................................................... 1 1 Introduction .......................................................................................................................................... 1 1.1 Motivation for the thesis .............................................................................................................. 1 1.2 Objective of the study .................................................................................................................. 2 1.3 Organization of the dissertation ................................................................................................... 2 Chapter 2 ....................................................................................................................................................... 4 2 Literature Review ................................................................................................................................. 4 2.1 Aluminum production chain ........................................................................................................ 4 2.1.1 Bayer process .......................................................................................................................... 4 2.1.1.1 Digestion ........................................................................................................................ 5 2.1.1.2 Clarification .................................................................................................................... 5 2.1.1.3 Precipitation .................................................................................................................... 5 2.1.1.4 Calcination ...................................................................................................................... 5 2.1.2 Lime – soda sintering process ................................................................................................. 5 2.2 Red mud ...................................................................................................................................... 6 2.2.1 Chemical and mineralogical characteristics of red mud .......................................................... 7 2.2.2 Negative effects of red mud .................................................................................................... 8 2.2.3 The possible applications of red mud ...................................................................................... 9 2.3 Hot metal ................................................................................................................................... 11 2.3.1 Pretreatment of hot metal ...................................................................................................... 12 2.4 Physicochemical properties of fluxes ........................................................................................ 14 2.4.1 Structural aspects of molten slags ......................................................................................... 14 2.4.2 Basicity definition ................................................................................................................. 16 vii 2.4.2.1 Common basicity indices ............................................................................................. 16 2.4.2.2 Optical basicity ............................................................................................................. 17 2.5 Desulphurization.......................................................................................................................
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