CHLORINATION FOR THE REMOVAL OF ZINC FROM BASIC OXYGEN STEELMAKING (BOS) BY-PRODUCT THESIS SUBMITTED FOR THE DEGREE OF DOCTOR OF PHILOSOPHY By IZAN JAAFAR BSc (Hons) – Env. Sc., MEng. (Env. M’ment) Institute of Sustainability and Environment, School of Engineering, Cardiff University 2014 1 DECLARATION This work has not previously been accepted in substance for any degree and is not concurrently submitted in candidature for any degree. Signed…………………………… (Izan Jaafar) Date ……………………..31/12/2013 STATEMENT 1 This thesis is being submitted in partial fulfilment of the requirements for the degree of PhD. Signed…………………………… (Izan Jaafar) Date……………………..31/12/2013 STATEMENT 2 This thesis is the result of my own independent work/investigation, except where otherwise stated. Other sources are acknowledged by explicit references. Signed……………………………(Izan Jaafar) Date……………………..31/12/2013 STATEMENT 3 I hereby give consent for my thesis, if accepted, to be available for photocopying and for inter-library loan and for the title and summary to be made available to outside organisations. Signed……………………………(Izan Jaafar) Date……………………..31/12/2013 i ABSTRACT A study on the chlorination of Basic Oxygen Steelmaking (BOS) by-product dusts followed by water leaching was conducted. The samples used for the studies sourced from the earth works and beneficiation of BOS byproduct from the stockpile. Comprehensive reports resulted from the excavation, beneficiation, physical and chemical analysis are reported. Zinc and iron removal studies from BOS by-product were investigated by means of chlorination roasting. Chlorination roasting of the BOS material by means of pyrometallurgical extraction was undertaking, assessing parameters such as roasting temperature, roasting time and chemical stoichiometry. A preliminary study was carried out using a solid chlorination agent, Ammonium Chloride (NH4Cl) in a muffle furnace for a 3 stage roasting conducted for 15 minutes to 180 minutes at 450C to 750C. Selected studies were carried out with 1-stage roasting. Further experimental studies then took place for chlorination using gaseous Cl2/N2 mixture gas in the tube furnace with 5 times chemical stoichiometry for a roasting time from 5 minutes to 90 minutes, with various temperatures from 150C to 750C. A 1 times and 2 times stoichiometry were added in selected procedure to foresee the effects of starvation agent. Additional surface area affects were also added to the chlorination with Cl2/N2 gas using bigger sample boat. Water leaching for 1 hour and 24 hours were conducted on the sample roasted with Cl2/N2 to investigate the leachability of Zn to assist further removal. The chemical and mineralogical composition of the BOS stockpile varied widely. The pH value were highly alkaline ranging from 10.2 – 13.5, while the moisture content showed a very wide range from 6 – 43%. The particle size analysis of the earth works excavation on the study site established five stockpile particle size fraction, ranging from as fine as <0.8mm to >38.22 mm. The composition of zinc ranging from 2.78% - 5.96%, while the iron content ranging from 41.36 to 62.18% respectively. This amount of iron has the potential for recovery and reused within a steel making process. It is possible to recover 97% of Zn and 30% Fe by roasting at 750C for a period of 135 minutes with NH4Cl salt. Roasting with 3 stages of NH4Cl addition proved to be more appropriate to increase the percentage of zinc removal. 97% Zn are removed Cl2/N2 gas for a period of 30 minutes roasting. The water leaching was conducted More than 90% Zn are recovered using bigger surface area sample boat with only 2.5 times stoichiometry. The extraction of Zn was greatly enhanced by the water leaching following the chlorination roasting using Cl2/N2 gas. 95% of Zn was leached while only 7% Fe was extracted after chlorination at 650C for 20 minutes roasting. It is possible to leach up to 98% Zinc after the chlorination roasting at 450C at 20 mins. The research has demonstrated that chlorination extraction has potential application in the steel sector for removal of Zn from steelmaking BOS dusts. In conducting the chlorination roasting, operational parameters such as temperature, roasting, chlorine agent stoichiometry, and surface area are important in determining the best operational condition. Hybrid process of chlorination roasting with leaching could highly assist in the further removal of Zn from BOS dust. ii DEDICATION To my beloved Baba & Mama; my inspiration iii ACKNOWLEDGEMENT I would like to express my sincere gratitude to my supervisor Prof Anthony Griffiths and Prof Keith Williams. The publication of this study would not be possible without their continuous supervision, guidance, encouragement and understanding. Their advices and suggestions have given a better insight into the completion of this research. I would like to express my great appreciation to the Ministry of Higher Education Malaysia and Universiti Malaysia Terengganu for their financial support to undertake this study. Not forgetting Tata Steel for the financial support particularly for the chemicals and experimental set up. Special thanks to Tata’s Centre of Excellence team in Cardiff University; Mr Julian Steer, Mr Andrew Hopkins and Mr Martyn Griffiths. I would also like to thank Mr Jeffrey Rowlands and Mr Ravi Mitha for all the help and assistance they provided me with in the CLEER laboratories throughout this study. I am grateful to Mr Malcolm Seabourne in particular and the remaining workshop technicians for the experimental set-up, rig design and rig development, ongoing advice and maintenance for the experimental works. I would also like to acknowledge all my fellow colleagues and friends who have been so encouraging for all these PhD years. Their valuable ongoing supports have motivates and inspires me to face all the turbulences and difficulties I’m facing in completing this research. Lastly, to my family, for their everlasting love, encouragement, motivation and believe in me. The accomplishment of this thesis would not be done without their continuous support. iv CONTENTS DECLARATION ................................................................................................................................ i ABSTRACT ....................................................................................................................................... ii DEDICATION .................................................................................................................................. iii ACKNOWLEDGEMENT ................................................................................................................ iv CONTENTS ....................................................................................................................................... v LIST OF FIGURES ......................................................................................................................... viii LIST OF TABLE .............................................................................................................................. xi LIST OF ABBREVIATIONS ......................................................................................................... xiii Chapter 1 INTRODUCTION .......................................................................................................... 1 1.1 Introduction ...................................................................................................................... 1 1.2 Aims and Objectives......................................................................................................... 5 1.3 Thesis Outline ................................................................................................................... 6 Chapter 2 LITERATURE REVIEW ............................................................................................ 10 2.1 Introduction .................................................................................................................... 10 2.2 STEELMAKING DUSTS .............................................................................................. 10 2.2.1 Formation ................................................................................................................. 11 2.2.2 Metallurgical and Characterization .......................................................................... 14 2.3 Sampling site investigation and sample beneficiation ................................................. 17 2.3.2 Sample Beneficiation ............................................................................................... 20 2.4 Extractive Metallurgy .................................................................................................... 22 2.4.1 Pyrometallurgy ......................................................................................................... 24 2.4.2 Hydrometallurgy ...................................................................................................... 26 2.5 CHLORINATION .......................................................................................................... 29 2.5.1 Introduction .............................................................................................................. 29 2.5.2 Mechanism ............................................................................................................... 31 2.5.3 Process design .........................................................................................................