lomeration of Iron Ores

Authored by

Ram Pravesh Bhagat

CRC PressTaylor& FrancisGroupBoca Raton London NewYork

CRC Press is an imprint of the

Taylor & Francis Group, an informa business

Table of Contents

Preface xix

Author Biography xxi

Acknowledgment xxiii

Chapter 1 Introduction 1

1.1 Preamble 1

1.2 Definition and Category 11.2.1 Agglomeration 11.2.2 Sintering 21.2.3 Peptizing 21.2.4 Briquetting 2

1.3 Scope of Agglomeration 31.4 Need for Agglomeration 31.5 Raw Materials for Agglomeration 41.6 The Agglomeration Processes 5

1.6.1 Sintering 51.6.2 Peptization 6

1.7 Iron Making 61.8 R&D 7

1.9 Techno-Economics 81.9.1 Sinter (Pellet) Plant Operation 81.9.2 Usage of Agglomerates 91.9.3 Reducing Operational Cost 91.9.4 Utilization of Slimes and Metallurgical

Wastes 10

1.10 Evolutionary Phases 101.10.1 Sintering 101.10.2 Peptization 11

References 11

Chapter 2 Raw Materials: Characterization and Preparation 13

2.1 Categories and Specifications 132.1.1 Iron Ore 13

2.1.2 Fluxes 14

2.1.3 Solid Fuel 16

2.1.4 Revert Materials/Metallurgical Wastes 162.1.5 Binders 17

2.2 Characterization of Raw Materials 18

2.3 Genesis of Iron Ore 18

vii

viii Table of Contents

2.4 Classification of Iron Ores 20

2.4.1 Hematite Ores 20

2.4.2 Magnetite Ore 21

2.4.3 GoethiteOre 21

2.4.4 Banded Hematite Quartzite/

Jasper (BHQ/BHJ) 22

2.5 Mineralogy of Iron Ores 23

2.5.1 Iron Ore-Bearing Minerals 23

2.5.2 Ores and Associated Minerals 24

2.5.3 Mineralogical Characterization 24

2.5.4 Liberation Characteristic of Minerals 26

2.6 Preparation of Ores and Other Raw Materials 28

2.6.1 Size Reduction and Size Classification 29

2.6.2 Beneficiation Process 32

2.6.3 Dewatering of Iron Ore Fines

and Slimes 36

2.7 Industrial Practice on Iron Ore Beneficiation

and Process Flow Sheets 37

2.7.1 Industrial Practice 37

2.7.2 Process Flow-sheet 39

2.7.3 Processing of Hematite Ores 42

2.7.4 Processing of Goethite Ore 44

2.7.5 Processing of Banded Hematite

Quartzite (BHQ) 45

2.7.6 Iron Ore Slimes 45

2.8 Handling of Iron Ores 48

References 49

Chapter 3 Iron-Making Processes 53

3.1 Preamble 53

3.2 Reduction of Iron Oxide 54

3.2.1 Sequential Steps of Reduction 54

3.2.2 Reduction Chemical Reactions 55

3.3 Direct Reduction Processes 56

3.3.1 Coal-Based Direct Reduction 56

3.3.2 Gas-Based Direct Reduction 57

3.4 Blast Furnace (BF) Iron-Making Process 58

3.4.1 Operation 59

3.4.2 Material Handling and Charging 59

3.4.3 Raw Materials 60

3.4.4 Products 61

3.5 Blast Furnace (BF) Iron-Making Reactions 63

3.5.1 Blast Furnace Zones: Reactions and Burden

Properties 63

3.5.2 Solution Loss Reaction and Shaft Efficiency 66

Table of Contents »*

3.6 Blast Furnace Performance: Factors Affecting 67

3.6.1 Chemical Composition of Burden Materials 67

3.6.2 Blast Furnace Burden 70

3.6.3 Size of Burden Materials and its Distribution 70

3.6.4 Cold Strength and Reduction Parameters of

Agglomerates 71

3.6.5 Permeability of the Stack Zone 72

3.6.6 Permeability in Cohesive Zone 75

3.6.7 Formation of Slag and its Characteristics 75

References 77

Chapter 4 Agglomerates in Iron-Making Processes 79

4.1 Preamble 79

4.2 Agglomerates in Iron-Making Processes 80

4.2.1 Iron Ore Pellets in Direct Reduction (DR) 80

4.2.2 Iron Ore Pellets in BF Iron Making 80

4.2.3 Iron Ore Sinter in BF Iron Making 83

4.3 Properties of Agglomerates 84

4.3.1 Cold Strength 84

4.3.2 Reduction Degradation Index (RDI) 84

4.3.3 Reducibility 85

4.3.4 Softening and Meltdown Characteristics 85

4.4 Quantitative Effect on Blast Furnace Performance 86

References 89

Chapter 5 Process of Sintering 91

5.1 Preamble 91

5.2 The Sintering Process 92

5.2.1 Description of a Sinter Plant 92

5.2.2 Raw Mix Preparation 93

5.2.3 Sintering Process 94

5.2.4 Cooling of Sinter and Downstream

Treatment 96

5.2.5 Power Consumption 96

5.3 Control of Sinter Plant Operation 97

5.4 Pollution Control and Waste Heat Recovery 99

5.4.1 Emission of Pollutants 99

5.4.2 Measures to Reduce Pollutants 100

5.4.3 Heat Recovery from Sinter Cooler 101

5.4.4 Emissions Optimized Sintering (EOS®)Process 101

5.5 Recycling of Steel Plant Solid Waste 103

5.5.1 Scope for Recycling 103

5.5.2 Characteristics of Metallurgical Wastes 103

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5.5.3 Mines and Metallurgical Wastes:

Categories and Functions 104

5.5.4 Economics of Recycling 107

5.6 Nonconventional/Other Processes 107

5.6.1 Hybrid Pelletized Sinter Process (HPS) 108

5.6.2 Pellet-Sintering 109

5.6.3 Composite AgglomerationProcess (CAP) 112

5.6.4 Mebios Process 113

5.6.5 New Charging Systems 114

5.6.6 High-Pressure Sintering 114

References 115

Chapter 6 Sintering Fundamentals 117

6.1 The Process of Sintering 117

6.1.1 Preamble 117

6.1.2 The Process 117

6.1.3 Characteristics of Sintering Process 119

6.2 Sintering Zones 119

6.3 Air Flow and Permeability 122

6.3.1 Permeability and Sintering Speed 122

6.3.2 Bed Permeability and Ergun's Equation 124

6.3.3 Application of Ergun's Equationto Sinter Mix Bed 125

6.4 Structure and Porosity of Bed 128

6.4.1 Bed Structure 128

6.4.2 Bed Porosity 129

6.5 Granules and Granulation 130

6.5.1 Effect of Granule Characteristics

on Productivity 130

6.5.2 Characteristics of Sinter Mix Granules 131

6.5.3 Granulation: Size Classification of Mix

Particles 132

6.5.4 The Granulation Process 134

6.5.5 Granulation Index 136

6.5.6 Granulation: Mechanism and Factors

Affecting 137

6.5.7 Moisture Content of Sinter Mix:

Effect on Granulation and Permeability 140

6.6 Thermal Characteristics During Sintering 141

6.6.1 Heat Transfer and Sintering Reactions 141

6.6.2 Heat Front and Flame Front 142

6.6.3 Speed of Flame Front 143

6.6.4 Gas Dynamics vis-a-vis Heat Patterns 144

Table of Contents Xl

6.6.5 Heat Pattern in Sintering versus

Sinter Quality 148

6.6.6 Burn-Through Point 149

6.7 Bonding in Sinter 150

6.8 Assimilation and Coalescence 151

6.8.1 Sintering of a Pseudo-Particle 151

6.8.2 Assimilation of Iron Ore 153

6.8.3 Assimilation of Fluxes 155

6.9 Sintering Reactions 156

6.9.1 Sintering: A Thermochemical Process 156

6.9.2 Mechanism of Sintering Reactions 156

6.9.3 Chemical Reactions (Basicity Effect) 158

6.10 Sintering Reaction and Mineralogy 159

6.10.1 Stages of Chemical Reactions 159

6.10.2 Sinter Mineralogy 160

6.10.3 Formation of SFCA 161

6.11 Mass Balance 161

6.11.1 Mass Balance in a Continuous

Sinter Plant 161

6.11.2 Charge Calculation 163

6.12 Heat Balance 163

6.13 Ignition 164

6.14 Combustion of Solid Fuel in Sintering 167

6.14.1 Effect of Combustion Behavior of Coke

on Sintering Indices 167

6.14.2 Combustion of Coke and Its Kinetics

during Sintering 167

6.14.3 Combustion of a Single Coke Particle 168

6.14.4 Association of Coke in Sinter Mix 169

6.14.5 Profile of Oxygen in Coke Combustion 170

6.14.6 Characteristics of Coke and UpstreamProcesses that Influence Coke Combustion 170

6.14.7 Combustion of Coke with Melts during

Sintering 172

6.14.8 Heating Value of Coke Combustion 173

6.14.9 Combustion Efficiency in Sintering 174

Annexures 175

AnnexureVI.l 175

Typical Calculation of Granule Characteristics

using Ergun's Equation 175

Annexure VI.2 177

Calculation of Sinter Charge 177

Annexure VI.3 179

Typical Calculation of Ignition Intensity 179

References 181

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Chapter 7 Sinter Productivity: Theoretical Considerationand Plant Practice 185

7.1 Sinter Productivity 185

7.1.1 Definition and Computation 185

7.1.2 Sintering Speed 186

7.1.3 Return Fines Recirculated 186

7.1.4 Parameters Affecting Sinter

Productivity 1887.2 Bed Permeability and Bed Structure 188

7.3 Iron Ores: Particle Size and Characteristics 190

7.3.1 Particle Size of Ores 190

7.3.2 Incorporation of Ultrafines 190

7.3.3 Ores: Textural Parameters and Chemical

Composition 191

7.3.4 Blending of Ores 1917.4 Granulation 192

7.4.1 Granule Size/Size Parameters

of Mix Ingredients 192

7.4.2 Bulk Density of Sinter Mix 192

7.4.3 Selective Granulation 193

7.4.4 Modification in Operational and MachineParameters 194

7.4.5 Usage of Lime 194

7.5 Moisture Content of the Sinter Mix 195

7.5.1 Role of Moisture in Granulation 196

7.5.2 Granulation with Low Moisture 197

7.5.3 Preheating of Sinter Mix 1987.6 Sinter Basicity and Mgo Content 199

7.6.1 Sinter Basicity 1997.6.2 Sinter MgO 199

7.7 Coke and Fluxes: Content, Nature,

and Particle Size 200

7.7.1 Nature of Solid Fuel and its Content 200

7.7.2 Particle Size of Coke and Flux 200

7.7.3 Split Addition Flux and Coke 200

7.8 Return Fines 201

7.8.1 Return Fines Regime 201

7.8.2 Return Fines Balance 202

7.8.3 Ratio (RO/RI) 203

7.8.4 Simulation of Return Fines Balance 204

7.8.5 Optimum of Return Fines 205

7.8.6 Carbon Equivalent of Return Fines 206

7.9 Sinter Mean Size 207

References 207

Table of Contents x'"

Chapter 8 Sinter Mineralogy 211

8.1 Preamble 211

8.2 Major Constituents and Desired Mineralogyof Sinter 212

8.3 Mineralogical Terminology 212

8.4 Sintering Reaction and Mineralogy 213

8.5 Composition and Mineralogical Characteristics

of Fluxed Sinter 214

8.5.1 Mineralogical Composition 214

8.5.2 Mineralogical Characteristics 215

8.6 Process Variables and Sinter Mineralogy 218

8.6.1 Flame Front Speed (FFS) 218

8.6.2 Cooling Rate 218

8.6.3 Bed Height 219

8.6.4 Return Fines 219

8.7 Sinter Chemistry and Its Mineralogy 219

8.7.1 Sinter Basicity 219

8.7.2 Fe Content in Sinter 220

8.7.3 Sinter Alumina 220

8.7.4 Sinter MgO 221

8.8 Sinter Mineralogy and Quality Parameters

of Sinter 221

8.8.1 Sinter Mineralogy 221

8.8.2 Sinter Porosity 221

8.8.3 Sinter Morphology 222

References 223

Chapter 9 Sinter Quality: Theoretical Consideration

and Plant Practice 225

9.1 Sinter Quality and Contributing Factors 2259.1.1 Quality Parameters 225

9.1.2 Contributing Factors in Sinter Quality 226

9.2 Sinter Mineralogy and Its Quality Parameters 228

9.2.1 Sinter Mineralogy 228

9.2.2 Sinter Porosity 230

9.2.3 Pore Size 231

9.2.4 Porous Morphology 231

9.3 Cold Strength 232

9.3.1 Strength of Sinter vis-A-vis Sintering

Speed 2329.3.2 Sinter Chemistry and Strength 233

9.3.3 Coke Addition 234

9.3.4 Bed Height 234

xiv Table of Contents

9.4 Sinter Reducibility 235

9.4.1 Nature of Ore and its Size 235

9.4.2 Sinter Chemistry 235

9.4.3 Operating Practices 2379.5 Sinter Reduction-Degradation Index (RDI) 237

9.5.1 Mechanism of Sinter RDI 237

9.5.2 Sinter Chemistry 238

9.5.3 Vertical Speed of Sintering 242

9.6 Salient Ways to Improve Sinter RDI 242

9.6.1 Sinter Alumina: Its Reduction

and Neutralization 242

9.6.2 Improving the Flux Size 2429.6.3 Split Addition of MgO-Bearing Fluxes 2439.6.4 Addition of Polymeric Additives 244

9.6.5 Inert Gas Injection 244References 244

Chapter 10 Process and Operational Variables with Respectto Sintering 249

10.1 Preamble 249

10.2 Iron Ore: Characteristics and Size Parameters 250

10.2.1 Chemical Composition 25010.2.2 Mineralogical and Morphological

Characteristics of Ores 251

10.2.3 Properties of Ores at Higher Temperature 25110.2.4 Size Parameters of Ores 251

10.2.5 Balling Characteristics of Ores 25110.3 Alumina Content of Ore 252

10.3.1 Sinter Mineralogy 25210.3.2 Effect of Alumina on Sinter Quality 252

10.3.3 Tackling the Adverse Effect of Alumina 25210.4 Sinter Basicity 255

10.5 Mgo Content of Sinter 256

10.5.1 Mineralogy and Quality of Sinter 256

10.5.2 High MgO Sintering Practice 257

10.5.3 Interinfluence of Sinter Basicity and Its

MgO Content vis-A-vis Coke Content 257

10.5.4 Alternate Resources of MgO 25 8

10.6 Fluxes: Size Parameters, Calcination,

and Assimilation 258

10.6.1 Particle Size of Flux 259

10.6.2 Calcination and Assimilation of Fluxes 259

10.6.3 Optimization of Crushing Scheme 262

10.7 Solid Fuel 263

10.7.1 Thermal Effect 263

Table of Contents xv

10.7.2 Size ofCoke and its Distribution 263

10.7.3 Mode of Coke Addition 265

10.7.4 Ash Content of Coke 266

10.7.5 Reduction in Specific Coke Consumption 267

10.7.6 Use of Alternate Fuels 269

10.8 Newer Coating And Granulation Techniques 270

10.8.1 Coating of Flux and Coke 270

10.8.2 Selective Granulation 272

10.9 Operating Practice 273

10.9.1 Moisture Content 273

10.9.2 Bed Height 274

10.9.3 Suction Pressure 274

10.9.4 Frequency of Machine Stoppages 27510.9.5 Stockpiling of Sinter 275

References 275

Chapter 11 Peptization Process 279

11.1 Peptization Process 279

11.2 Raw Materials and Their Preparation 279

11.2.1 Iron Ore 280

11.2.2 Fluxes 280

11.2.3 Solid Fuel 281

11.2.4 Binders 281

11.3 Peptization Steps 282

11.3.1 Mixing 282

11.3.2 Peptization (Balling) 282

11.3.3 Induration 283

11.4 Pollution Control and Energy Conservation 283

11.4.1 Emission of Pollutants 283

11.4.2 Removal of Pollutants 284

11.4.3 Energy Conservation 284

11.5 Specifications of Pellet Plants 28511.6 Composite Pellets 285

References 286

Chapter 12 Green Peptization: Process and Mechanism 289

12.1 Balling Process 28912.1.1 Peptizing Units: Description

and Operation 28912.1.2 Operation of Rotating Device 292

12.1.3 Material Movement in a Balling Unit 293

12.1.4 Drum versus Disc Peptizer 295

12.2 Formation of Green Balls and Growth 296

12.2.1 Formation of Green Balls 296

icvi Table of Contents

12.2.2 Growth of Balls 296

12.2.3 Role of Moisture in Granulation 297

12.2.4 Forces Involved in Formation

of Green Balls 298

12.2.5 Stages of Granulation in Green

Pelletization 300

12.3 Strength of Wet Agglomerates 302

12.3.1 Capillary Theory for Wet Agglomerate

Strength 302

12.3.2 Rumpf's Equation for Agglomerate

Strength 30312.3.3 Influencing Parameters for Agglomerate

Strength 305

12.4 Viscosity Effect and Binders 308

12.4.1 Viscosity Effect 308

12.4.2 Binders 308

12.4.3 Requirements of Binders 31012.4.4 Bentonite (as Binder) 31012.4.5 Ball-Ability 313

12.5 Elastic and Plastic Deformation of Green Pellets 313

12.6 Stages of Pellet Formation and Growth 31512.7 Kinetics of Ball Growth 317

12.7.1 Stages of Kinetics 31712.7.2 Kinetic Equation for Pellet Growth 319

12.7.3 Factors Influencing the Ball Growth 320

References 323

Chapter 13 Quality of Green Pellets 327

13.1 Preamble 327

13.2 Size and Porosity of Pellets 328

13.3 Drop Resistance (Number) 32913.4 Wet Compressive Strength 331

References 333

Chapter 14 Induration of Green Pellets 335

14.1 Preamble 335

14.2 Pellet Induration: Steps 33614.2.1 Drying 33614.2.2 Preheating 33814.2.3 Firing 33914.2.4 Cooling 340

14.3 Process of Induration Using Shaft Furnace 34014.4 Straight-Grate Process of Pellet Induration 341

14.4.1 Straight-Grate System 341

Table of Contents xvii

14.4.2 Zones of Induration 343

14.4.3 Characteristic Features of Straight-Grate

System 344

14.4.4 Heat Recovery in Straight-Grate System 345

14.5 Grate-Kiln-Cooler Process 345

14.5.1 Grate-Kiln-Cooler System 345

14.5.2 Design Parameters 347

14.5.3 Operation 348

14.5.4 System of Heat Recuperation 350

14.5.5 Deposit Formation 350

14.5.6 Characteristic Features 351

14.6 Comparison of Straight-Grate Process Vis-A-Vis

Grate-Kiln Process 351

14.7 Factors Influencing the Induration Process

(and Pellet Quality) 353

14.8 Fuel Substitution in Pellet Induration 356

14.8.1 Coal Injection 35714.8.2 Nature of Carbonaceous Materials 357

14.8.3 Utilization of DR Coal Fines 357

14.8.4 Developed Technologies 358

14.8.5 Problems and Solutions 358

References 358

Chapter 15 Reactions and Formation of Phases During Induration

of Pellet 361

15.1 Preamble 361

15.2 Induration of Magnetite-Bearing Pellets

and Phases Formed 362

15.2.1 Reactions with Magnetite Concentrate 362

15.2.2 Phases Formed 363

15.3 Induration of Hematite-Bearing Pellets andPhases Formed 364

15.4 Induration: Magnetite Vis-A-Vis Hematite

Concentrate 365

15.5 Phases and Pores in Indurated Pellets 366

15.5.1 Bonding and Phases 36615.5.2 Formation of Pores 367

15.6 Parameters Influencing the Mineral Phases

in Indurated Pellets 367

15.6.1 Pellet Basicity 367

15.6.2 Addition of Coke 369

15.6.3 Bentonite Dosage 36915.7 Parameters Influencing the Porosity in Indurated

Pellets 370

15.7.1 Effect of Pellet Basicity and MgO Content 370

xviii Table of Contents

15.8 Duplex Structure 371

15.8.1 Formation of Duplex Structure 371

15.8.2 Mechanism of Formation 372

15.8.3 Ways to Minimize the Duplex Structure 373

References 373

Chapter 16 Quality of Indurated Pellets 375

16.1 Preamble: Pellet Properties and Factors Influencing 375

16.1.1 Pellet Properties 375

16.1.2 Textural Characteristics and Pellet Properties 375

16.1.3 Factors Affecting Pellet Properties 376

16.2 Pellet Chemistry 376

16.3 Bulk Density and Angle of Repose 377

16.4 Crushing Strength 377

16.4.1 Raw Materials (Including Binders)and Their Characteristics 377

16.4.2 Induration Conditions 382

16.5 Porosity 384

16.6 Swelling Index 385

16.7 Pellet Reducibility 388

16.8 Reduction-Degradation Index (RDI) 389

16.9 Softening And Meltdown Characteristics 389

References 390

Annexures 393

Annexure 1 393

Annexure II 394

Test Methods for Quality Parameters of Sinter

and Pellets 394

Preamble 394

Sampling and Sample Preparation 394

Green Pellets 395

Indurated Pellets 395

Swelling Index (SI) 396

Clustering Index 397

Sinter/Pellets 398

Organizations of Standards Referred 403

References 403

Index 405