HEAT TREATMENT OF IRON ORE AGGLOMERATES WITH MICROWAVE ENERGY A THESIS SUBMITTED TO THE GRADUATE SCHOOL OF NATURAL AND APPLIED SCIENCES OF MIDDLE EAST TECHNICAL UNIVERSITY BY ÇİĞ DEM ÇIRPAR IN PARTIAL FULFILLMENT OF THE REQUIREMENTS FOR THE DEGREE OF MASTER OF SCIENCE IN MINING ENGINEERING JANUARY 2005 Approval of the Graduate School of Natural and Applied Sciences Prof. Dr. Canan Özgen Director I certify that this thesis satisfies all the requirements as a thesis for the degree of Master of Science/Arts / Doctor of Philosophy. Prof. Dr. Ümit Atalay Head of Department This is to certify that we have read this thesis and that in our opinion it is fully adequate, in scope and quality, as a thesis for the degree of Master of Science. Prof. Dr. Ali İhsan Arol Supervisor Examining Committee Members Prof. Dr.Gülhan Özbayo ğlu (METU,MINE) Prof. Dr. Ali İhsan Arol (METU,MINE) Prof. Dr. Ümit Atalay (METU,MINE) Prof. Dr. Çetin Ho şten (METU,MINE) Prof. Dr. Yavuz Topkaya (METU,METE) I hereby declare that all information in this document has been obtained and presented in accordance with academic rules and ethical conduct. I also declare that, as required by these rules and conduct, I have fully cited and referenced all material and results that are not original to this work. Name, Last name: Çi ğdem Çırpar Signature : ABSTRACT HEAT TREATMENT OF IRON ORE AGGLOMERATES BY MICROWAVE ENERGY Çırpar, Çi ğdem M.Sc., Department of Mining Engineering Supervisior: Prof.Dr. Ali İhsan Arol January, 2005, 90 pages Pelletizing is a size enlargement technique employed to process fine-grained iron-bearing concentrates and powder ores. Mechanical strength of fired pellets is important for handling. When the pellets undergo metallurgical processing, their mechanical strength is a measure of their resistance to degradation by breakage due to impacts and abrasion to which they are exposed in the upper part of the blast furnace. In this study, heat treatment of iron ore agglomerates with microwave energy is investigated. First drying and then heat hardening tests were performed. Two main properties of pellets were taken into consideration: percent moisture and magnetite content for the dried pellets and compressive strength and also magnetite content for the fired pellets. The tests were conducted with different particle sized pellets, in different durations. In order to increase the oxidation rate in heat hardening tests, Na 2O2 is also added in different percentages. The results of the study showed that, magnetite pellets can indeed be dried and heated with microwave energy. However, the attained compressive strength and iv the oxidation of the fired pellets were not sufficient as compared to pellets produced by conventional heating Keywords: microwaves, iron ore, magnetite, pelletizing, agglomerates v ÖZ DEM İR CEVHER İ AGLOMERELER İNİN M İKRODALGA ENERJ İSİ İLE ISITILMASI Çırpar, Çi ğdem Yüksek Lisans, Maden Mühendisli ği Bölümü Tez Yöneticisi: Prof.Dr. Ali İhsan Arol Ocak, 2005, 90 pages Peletleme, ince tane boyunda demir içeren konsantrelerin ve toz halindeki cevherlerin i şlenmesinde kullanılan bir boyut büyütme yöntemidir. Pi şirilmi ş peletlerin mekanik dayanımları ta şınma sırasında önemlidir. Peletler metalurjik işlemlere tabi tutulduklarında, mekanik dayanımları onların yüksek fırının üst kısımlarında maruz kaldıkları çarpmaların ve a şındırmaların sebep oldu ğu bozulma ve kırılmalara dayanımlarının ölçüsüdür. Bu çalı şmada, demir cevheri aglomeratlarının mikrodalga enerjisi ile ısıtılması ara ştırılmı ştır. İlk olarak kurutma, daha sonra ısıyla sertle ştirme testleri yapılmı ştır. Kurutulmu ş peletler için nem yüzdesi ve manyetit oranı, pi şirilmi ş peletler için basma dayanımları ve yine manyetit oranı dikkate alınmı ştır. Deneyler farklı tane boyundaki peletlerle, farklı i şlem sürelerinde gerçekle ştirilmi ştir. Sertle ştirilme deneylerinde yükseltgenme oranının arttırılması için peletlere farklı oranlarda Na 2O2 eklenmi ştir. Çalı şmanın sonuçları göstermi ştir ki, manyetit peletler mikrodalga enerjisi ile kurutulup, ısıtılabilmi ştir. Fakat pi şirilen peletlerde ula şılan sıkı şma dayanımı vi ve yükseltgenme geleneksel ısıtma i şlemlerinle kar şıla ştırıldı ğında yeterli de ğildir. Anahtar Kelimeler: Mikrodalga, demir cevheri, manyetit, peletleme, aglomerat. vii To My Parents, Who Always Support Me To Make My Dreams Come True… viii ACKNOWLEDGEMENTS I want to express my sincerest and endless appreciation to my advisor Prof.Dr. Ali İhsan Arol for his kind supervision, guidance, suggestions, comments, help, and friendly attitude throughout this study. I also wish to express my appreciation to Prof. Dr. Ümit Atalay for his suggestions and comments. I gratefully acknowledge Tuncer Gençtan, Süleymen Kırıcı, Mehmet Çakır, Tahsin I şıksal, İsmail Kaya for their kindness, friendly attitude, and technical support. I would also like to express my thanks to my friends Burcu Ardıço ğlu who was always by my side these six years and being my dreamsharer, Tu ğcan Tuzcu, Filiz Toprak, Hamdaweh Suleymana, Sava ş Özün, Osman Sivrikaya, Mehtap Gülsün, Sinan İnal and Ömer Can Özcan for their help, comments, encouragement through the hard times during the study, and for their friendship… Special thanks are also extended to my friend Ziya Ö ğütcü for being by my side during my trials and tribulations and assuring me, when I was most hopeless, that good days were yet to come. Finally, my endless and profound thanks and love would go to my parents, my aunt for her role as the substitute mother, and my brother and his family with the new comer Ada. All the beauties, values and happiness they bring to my life and the love they give to me without any expectations make me the luckiest person in the world. ix TABLE OF CONTENTS PLAGIARISM…………………………………………………………… iii ABSTRACT……………………………………………………………… iv ÖZ………………………………………………………………………… vi DEDICATION…………………………………………………………… viii ACKNOWLEDGEMENTS……………………………………………... ix TABLE OF CONTENTS……………………………………………...... x LIST OF TABLES……………………………………………………..... xiii LIST OF FIGURES……………………………………………………... xv LIST OF ABREVIATIONS…………………………………………...... xviii CHAPTER 1. INTRODUCTION……………………………………………… 1 2. LITERATURE SURVEY……………………………………… 4 2.1 Pelletizing…………………………………………………... 4 2.1.1 General Principles of Pelletizing………………….… 4 2.1.1.1 Balling……………………………………… 4 2.1.1.2 Properties of Material for Balling…………... 4 2.1.1.3 Binders……………………………………… 7 2.1.1.4 Requirements for Ball Properties…………… 9 2.1.2 Hardening of Pellets………………………………… 11 2.1.2.1 Drying……………………………………… 11 2.1.2.2 Theory of Pellet Hardening………………… 12 2.1.2.3 Heat Hardening by Oxidation……………… 15 2.1.2.4 Hardening by Reduction…………………… 16 2.1.2.5 Low-Temperature Hardening Treatments… 17 2.1.3 Requirements for Pellet Properties………………… 17 2.1.4 Conventional Equipments Used to fire Pellets……... 18 2.1.4.1 Shaft Furnaces……………………………… 18 2.1.4.2 Horizontal Traveling Grate Process………… 19 x 2.1.4.3 The Grate-Kiln Process…………………… 19 2.2 Theory of Microwave Heating…………………………… 20 2.2.1 Basic Concept of Microwave Energy……………… 20 2.2.2 Working Principles of Microwave Oven………… 24 2.2.3 Early History of Microwave Oven………………… 26 2.2.4 Applications of Microwave Processing…………… 27 2.2.5 Advantages of Microwave Heating……………… 28 2.2.6 Microwave Energy for Mineral Treatment Processes............................................................................ 30 2.2.6.1 Microwave Heating of Minerals……………. 30 2.2.6.2 Microwave Assisted Ore Grinding…………. 39 2.2.6.3 Microwave Assisted Carbothermic Reduction of Metal Oxide………………….. 40 2.2.6.4 Microwave Assisted Drying and Anhydration 40 2.2.6.5 Microwave Assisted Mineral Leaching……. 41 2.2.6.6 Microwave Assisted Roasting and Smelting of Sulphide Concentrate……………………. 41 2.2.6.7 Microwave Assisted Pretreatment of Refractory Gold Concentrate……………….. 42 2.2.6.8 Microwave Assisted Coal Desulphurization... 42 2.2.6.9 Microwave Assisted Spent Carbon Regeneration………………………………... 43 2.2.6.10 Microwave Assisted Waste Management…. 43 2.3 Iron Ore…………………………………………………….. 43 3. MATERIALS AND METHODS………………………………. 45 3.1 Materials…………………………………………………… 45 3.2 Methods………………………………………………......... 45 3.2.1 Density Measurement………………………………. 45 3.2.2 Specific Area Measurement………………………… 46 3.2.3 Preparation of Magnetite Disk Pellets……………… 47 3.2.4 Drying and Hardening Tests………………………... 48 xi 4. RESULTS AND DISCUSSION………………………………... 52 4.1 Drying Characteristics of Magnetite Pellets with Microwave Oven………………………………………………. 52 4.2 Heating Characteristics of Magnetite Pellets with Microwave Oven……………………………………………… 58 4.2.1 Heating Characteristics of Magnetite Pellets with Addition of Na 2O2....................................................... 65 5. CONCLUSION…………………………………………………. 67 REFERENCES…………………………………………………………... 69 APPENDICES A. Air Permeability Apparatus Manual……………………………….. 73 B. Weight loss, %Fe 3O4 and Compressive Strength Tables………….. 80 xii LIST OF TABLES TABLE 1. Moisture on balling various types of materials………………………… 6 2. Effect of mineralogical composition on particle shape………………… 7 3. Microwave heating of some oxides and sulphides compounds………... 31 4. Classification of some reagents grade materials based on microwave heating rate………………………………………………………………. 32 5. Mineral transparent to microwave irradiation (2450 MHz, 150 W, 5 min exposure)……………………………………………………………. 33 6. Results of microwave heating of ores (2450 MHz, 3-5 min exposure).. 34 7. Effect of microwave heating on the temperature of natural minerals…. 36 8. Effect of microwave heating on the temperature of reagent