Innovation in Electric Arc Furnaces (eBook)

Preface 5
Contents 6
Introduction 12
1 Modern Steelmaking in Electric Arc Furnaces: History and Prospects for Development 16
1.1 General Requirements for Steelmaking Units 16
1.1.1 Process Requirements 16
1.1.2 Economic Requirements 17
1.1.3 Environmental and Health and Safety Requirements 20
1.2 High-Power Furnaces: Issues of Power Engineering 21
1.2.1 Maximum Productivity as the Key Economic Requirement to EAF 21
1.2.2 Increasing Power of EAF Transformers 22
1.2.3 Specifics of Furnace Electrical Circuit 23
1.2.4 Optimum Electrical Mode of the Heat 26
1.2.5 DC Furnaces 28
1.2.6 Problems of Energy Supply 28
1.3 The Most Important Energy and Technology Innovations 29
1.3.1 Intensive Use of Oxygen, Carbon, and Chemical Heat 29
1.3.2 Foamed Slag Method 30
1.3.3 Furnace Operation with Hot Heel 31
1.3.4 Use of Hot Metal and Reduced Iron 32
1.3.5 Single Scrap Charging 32
1.3.6 Post-combustion of CO Above the Bath 33
1.4 Outlook 35
1.4.1 World Steelmaking and Mini-mills 35
1.4.2 The Furnaces of a New Generation 35
1.4.3 Consteel Process 37
References 38
2 Electric Arc Furnace as Thermoenergetical Unit 39
2.1 Thermal Performance of Furnace: Terminology and Designations 39
2.2 External and Internal Sources of Thermal Energy: Useful Heat 41
2.3 Factors Limiting the Power of External Sources 42
2.4 Key Role of Heat Transfer Processes 43
Reference 44
3 The Fundamental Laws and Calculating Formulae of Heat Transfer Processes 45
3.1 Three Ways of Heat Transfer: General Concepts 45
3.2 Conduction Heat Transfer 46
3.2.1 Fourier--s Law. Flat Uniform Wall. Electrical--Thermal Analogy 46
3.2.2 Coefficient of Thermal Conductivity 49
3.2.3 Multi-layer Flat Wall 52
3.2.4 Contact Thermal Resistance 53
3.2.5 Uniform Cylindrical Wall 54
3.2.6 Multi-layer Cylindrical Wall 55
3.2.7 Simplifying of Formulae for Calculation of Cylindrical Walls 56
3.2.8 Bodies of Complex Shape: Concept of Numerical Methods of Calculating Stationary and Non-stationary Conduction Heat Transfer 57
3.3 Convective Heat Exchange 60
3.3.1 Newtons Law: Coefficient of Heat Transfer 61
3.3.2 Two Modes of Fluid Motion 61
3.3.3 Boundary Layer 62
3.3.4 Free (Natural) Convection 63
3.3.5 Convective Heat Transfer at Forced Motion 64
3.3.6 Heat Transfer Between Two Fluid Flows Through Dividing Wall Heat Transfer Coefficient k
3.4 Heat Radiation and Radiant Heat Exchange 70
3.4.1 General Concepts 70
3.4.2 Stefan--Boltzmann Law Radiation Density
3.4.3 Heat Radiation of Gases 74
3.4.4 Heat Exchange Between Parallel Surfaces in Transparent Medium: Effect of Screens 75
3.4.5 Heat Exchange Between the Body and Its Envelope: Transparent Medium 76
3.4.6 Heat Exchange Between the Emitting Gas and the Envelope 77
4 Energy (Heat) Balances of Furnace 79
4.1 General Concepts 79
4.2 Heat Balances of Different Zones of the Furnace 80
4.3 Example of Heat Balance in Modern Furnace 82
4.4 Analysis of Separate Items of Balance Equations 83
4.4.1 Output Items of Balance 84
4.4.2 Input Items of Balance 86
4.5 Chemical Energy Determination Methods 87
4.5.1 Utilization of Material Balance Data 87
4.5.2 About the So-Called ''Energy Equivalent'' of Oxygen 88
4.5.3 Calculation of Thermal Effects of Chemical Reactions by Method of Total Enthalpies 89
References 94
5 Energy Efficiency Criteria of EAFs 95
5.1 Preliminary Considerations 95
5.2 Common Energy Efficiency Coefficient of EAF and Its Deficiencies 97
5.3 Specific Coefficients for Estimation of Energy Efficiency of Separate Energy Sources and EAF as a Whole 98
5.4 Determining Specific Coefficients 101
5.4.1 Electrical Energy Efficiency Coefficient 0 EL 102
5.4.2 Fuel Energy Efficiency Coefficient of Oxy-gas Burners 0 NG 103
5.4.3 Energy Efficiency Coefficient of Coke Charged Along with Scrap 104
5.4.4 Determining the Specific Coefficients by the Method of Inverse Heat Balances 105
5.5 Tasks of Practical Uses of Specific Coefficients 105
References 106
6 Preheating of Scrap by Burners and Off-Gases 107
6.1 Expediency of Heating 107
6.2 Consumptions of Useful Heat for Scrap Heating, Scrap Melting, and Heating of the Melt 108
6.3 High-Temperature Heating of Scrap 109
6.3.1 Calculation of Potential of Electrical Energy Savings 109
6.3.2 Sample of Realization: Process BBC--Brusa 110
6.4 Specifics of Furnace Scrap Hampering Its Heating 111
6.5 Processes of Heating, Limiting Factors, Heat Transfer 112
6.5.1 Two Basic Methods of Heating 112
6.5.2 Heating a Scrap Pile in a Large-Capacity Container 113
6.5.3 Heating on Conveyor 116
6.6 Devices for Heating of Scrap: Examples 119
6.6.1 Heating in Charging Baskets 119
6.6.2 DC Arc Furnace Danarc Plus 122
6.6.3 Shaft Furnaces 124
6.6.4 Twin-Shell Steelmelting Units 125
References 127
7 Replacement of Electric Arcs with Burners 128
7.1 Attempts for Complete Replacement 128
7.2 Potentialities of Existing Burners: Heat Transfer, Limiting Factors 130
7.3 High-Power Rotary Burners (HPR-Burners) 132
7.3.1 Fundamental Features 133
7.3.2 Two-Stage Heat with HPR-Burners 133
7.4 Industrial Trials of HPR-Burners 135
7.4.1 Slag Door Burners: Effectiveness of Flame Direction Changes 135
7.4.2 Two-Stage Process with a Door Burner in 6-ton Furnaces 137
7.4.3 Two-Stage Process with Roof Burners in 100-ton and 200-ton EAFs 140
7.5 Oriel and Sidewall HPR-Burners 144
7.6 Fuel Arc Furnace (FAF) 148
7.7 Economy of Replacement of Electrical Energy with Fuel 150
References 152
8 Basic PhysicalChemical Processes in Liquid Bath: Process Mechanisms 154
8.1 Interaction of Oxygen Jets with the Bath: General Concepts 154
8.2 Oxidation of Carbon 155
8.3 Melting of Scrap 157
8.4 Heating of the Bath 159
9 Bath Stirring and Splashing During Oxygen Blowing 161
9.1 Stirring Intensity: Methods and Results of Measurement 161
9.2 Mechanisms of Bath Stirring 162
9.2.1 Stirring Through Circulation and Pulsation 162
9.2.2 Stirring by Oxygen Jets and CO Bubbles 163
9.3 Factors Limiting Intensity of Bath Oxygen Blowing in Electric Arc Furnaces 164
9.3.1 Iron Oxidation: Effect of Stirring 164
9.3.2 Bath Splashing 166
9.4 Oxygen Jets as a Key to Controlling Processes in the Bath 168
References 169
10 Jet Streams: Fundamental Laws and Calculation Formulae 170
10.1 Jet Momentum 170
10.2 Flooded Free Turbulent Jet: Formation Mechanism and Basic Principles 171
10.3 Subsonic Jets: Cylindrical and Tapered Nozzles 173
10.4 Supersonic Jets and Nozzles: Operation Modes 176
10.5 Simplified Formulae for Calculations of High-Velocity Oxygen Jets and Supersonic Nozzles 178
10.5.1 A Limiting Value of Jets' Velocity 180
10.6 Long Range of Jets 181
Reference 181
11 Devices for Blowing of Oxygen and Carbon into the Bath 182
11.1 Blowing by Consumable Pipes Submerged into Melt and by Mobile Water-Cooled Tuyeres 182
11.1.1 Manually Operated Blowing Through Consumable Pipes 183
11.1.2 BSE Manipulator 183
11.1.3 Mobile Water-Cooled Tuyeres 185
11.2 Jet Modules: Design, Operating Modes, Reliability 187
11.2.1 Increase in Oxygen Jets Long Range: Coherent Jets 189
11.2.2 Effectiveness of Use of Oxygen, Carbon, and Natural Gas in the Modules 192
11.3 Blowing by Tuyeres Installed in the Bottom Lining 194
11.3.1 Converter-Type Non-water-Cooled Tuyeres 194
11.3.2 Tuyeres Cooled by Evaporation of Atomized Water 195
11.3.3 Explosion-Proof Highly Durable Water-Cooled Tuyeres for Deep Blowing 198
References 202
12 Water-Cooled Furnace Elements 203
12.1 Preliminary Considerations 203
12.2 Thermal Performance of Elements: Basic Laws 203
12.3 Principles of Calculation and Design of Water-Cooled Elements 207
12.3.1 Determining of Heat Flux Rates 207
12.3.2 Minimum Necessary Water Flow Rate 209
12.3.3 Critical Zone of the Element 210
12.3.4 Temperature of Water-Cooled Surfaces 210
12.3.5 Temperature of External Surfaces 212
12.3.6 General Diagram of Element Calculation 214
12.3.7 Hydraulic Resistance of Elements 214
12.4 Examples of Calculation Analysis of Thermal Performance of Elements 217
12.4.1 Mobile Oxygen Tuyere 217
12.4.1.0 Input Data 217
12.4.1.0 Calculation of Basic Parameters of Thermal Performance of Tuyere 218
12.4.2 Elements with Pipes Cast into Copper Body and with Channels 219
12.4.2.0 Input Data 220
12.4.2.0 Calculation of the Basic Parameters of Thermal Performance of the Element 220
12.4.3 Jet Cooling of the Elements 222
12.4.4 Oxygen Tuyere for Deep Blowing of the Bath 223
12.4.4.0 Calculation of Basic Parameters of Thermal Performance of the Tuyere 224
References 225
13 Principles of Automation of Heat Control 226
13.1 Preliminary Considerations 226
13.2 Automated Management Systems 226
13.2.1 Use of Accumulated Information: Static Control 226
13.2.2 Mathematical Simulation as Method of Control 227
13.2.3 Dynamic Control: Use of On-line Data 230
13.3 Rational Degree of Automation 236
References 237
14 Off-gas Evacuation and Environmental Protection 238
14.1 Preliminary Considerations 238
14.2 Formation and Characteristics of DustGas Emissions 238
14.2.1 Sources of Emissions 238
14.2.2 Primary and Secondary Emissions 239
14.2.3 Composition, Temperature, and Heat Content of Off-gases 240
14.3 Capturing Emissions: Preparing Emissions for Cleaning in Bag Filters 242
14.3.1 General Description of the System 242
14.3.2 Problems of Toxic Emissions 243
14.3.3 A Simplified Method of Gas Parameters' Calculation in the Direct Evacuation System 245
14.4 Calculations 246
14.3.3 List of Designations 246
14.3.3.0 Amount of CO Evolving from Bath , m 3 /min 247
14.3.3.0 Amount of Combustion Products Generated by Burners 248
14.3.3.0 Amount of Primary Air Infiltrated into Freeboard, m 3 /min 248
14.3.3.0 Maximum Amount of Primary Gases at the Outlet of the Roof Elbow, m 3 /min 249
14.3.3.0 Composition of Primary Gases, 0 249
14.3.3.0 The Temperature of Primary Gases , C 250
14.3.3.0 Physical Heat Content of Primary Gases 250
14.3.3.0 Amount of Gases at the Inlet of the Stationary Gas Duct (Cross-Section 202) , m 3 /min 251
14.3.3.0 Temperature of Gas Mixture with Air at the Inlet of the Stationary Gas Duct 251
14.3.3.0 Amount of Gases After Secondary Post-combustion in the Stationary Gas Duct, , m 3 /min 252
14.3.3.0 Composition of Humid Gases After Secondary Post-combustion, 0 252
14.3.3.0 Total Heat Content and Temperature of Gases After Secondary Post-combustion , C 252
14.3.3.0 Negative Pressure at the Inlet of the Stationary Gas Duct Necessary for Prevention of Uncontrolled Emissions Through the Electrode Ports 253
14.3.4 Energy Problems 255
14.4 Use of Air Curtains 257
References 261
Index 262