Electric Arc Furnace with Flat Bath (eBook)

Contents 6
Introduction 9
1 Modern EAFs and Technology of the Heat with Continuous Charging of Scrap into Flat Bath 11
Abstract 11
1.1 Performances of Furnaces Operating on Scrap 11
1.2 Use of Hot Metal 12
1.3 The Most Important Technology and Energy Innovations Allowing to Achieve Current EAF’s Performances 13
1.3.1 Out-of-Furnace Metal Processing at Ladles 13
1.3.2 Increasing Power and Furnace Capacity 13
1.3.3 Optimal Electrical Mode of the Heat 14
1.3.4 Foamed Slag Method 16
1.3.5 Furnace Operation with Hot Heel 18
1.3.6 Intensive Use of Oxygen, Carbon and Chemical Heat 19
1.3.7 Single Scrap Charging 20
1.4 Most Important Design Innovations 21
1.4.1 Optimization of Freeboard Dimensions 21
1.4.2 Slagless Tapping System 23
1.4.3 Electrode Holders with Current-Conducting Arms and Gantry-Less Design of EAFs 24
1.4.4 Speeding-Up of EAF’s Drives and Shortening of Power-Off Times 25
1.5 Change of Method of Scrap Charging as a Pre-requisite for Improvement of Main Performances of EAF 25
1.5.1 Increase in Productivity 25
1.5.2 Reduction of Electrical Energy Consumption 27
1.6 Flat Bath Method with Continuous Scrap Charging 31
1.6.1 Key Features 31
1.6.2 Potentialities 31
References 33
2 Implementation of New Technology 34
Abstract 34
2.1 Predecessors 34
2.2 Conveyor Furnaces 38
2.2.1 Design and Technological Process 38
2.2.2 Comparison Between Conveyor Furnaces and Modern EAFs 41
2.3 Shaft Furnaces 44
2.3.1 Furnaces with Fingers Retaining Scrap 44
2.3.2 Shaft Furnaces with Pushers 46
2.3.3 Ecological Problems 50
2.4 Results of the Implementation 51
References 52
3 Scrap Melting Process in Liquid Metal 53
Abstract 53
3.1 Preliminary Comments 53
3.2 Melting a Scrap with and Without Carbon Diffusion 54
3.3 Convection as Basic Melting Process Without Contribution of Carbon Diffusion 55
3.3.1 Definition of Convection Heat Transfer Coefficient
3.3.2 Two Modes of Fluid Motion 56
3.3.3 Boundary Layer 56
3.3.4 Bath Stirring 57
3.3.5 Free and Forced Convection 59
3.3.6 Features of Convection in Liquid Metals 62
3.4 Melting in Liquid Steel Experimental Data
3.4.1 Melting of Individual Piece of Scrap with Solidified Layer 63
3.4.2 Melting Without Solidified Layer 68
3.4.3 Simultaneous Melting of Multiple Scrap Pieces 70
3.5 How to Accelerate Melting Analysis of Options
3.5.1 Increasing Heat Transfer Coefficient ? 72
3.5.2 Increasing Volume of Charging Zone 74
3.5.3 Scrap Preheating 74
References 75
4 Methods of Realization of High-Temperature Scrap Preheating 76
Abstract 76
4.1 Specifics of Furnace Scrap Associated with Its Heating 76
4.2 Selection of the Furnace Type 77
4.2.1 Conveyer or Shaft Furnace 77
4.2.2 Shaft Furnaces with Scrap Retaining Fingers (QUANTUM-Type) or Furnaces with Scrap Pushers (COSS-Type) 78
4.3 Selection of the Energy Source 79
4.3.1 Off-Gases Insufficient Heat Power of the Flow
4.3.1.1 Calculation 80
4.3.2 Combined Use of Off-Gases and Burners Dead-End with Regard to Energy
4.3.3 Scrap Preheating by Burners Only: Replacement of Electrical Energy with Energy from Fuel 82
4.3.3.1 Calculation 82
4.4 The System of High-Temperature Scrap Preheating in the Furnace Shaft by Means of Oxy-gas Recirculation Burner Devices 85
4.4.1 Key Features, Design and Operation of the System 85
4.4.2 Gas Evacuation and Environment 88
References 89
5 Increasing Scrap Melting Rate by Means of Bath Blowing 90
Abstract 90
5.1 Purpose of Blowing 90
5.2 Selection of Methods and Means of Blowing 91
5.2.1 Jet Modules 91
5.2.2 Converter Type Bottom Tuyeres 94
5.2.3 Tuyeres Cooled by Evaporation of Atomized Water 96
5.2.4 Mobile Water Cooled Tuyeres 100
5.3 Principles of Design and Calculation of Highly Durable Water Cooled Tuyeres 102
5.3.1 Heat Operation of Tuyeres, Fundamental Dependences, Heat Flows, and Temperatures 102
5.3.2 Cooling of Tuyeres with Local Water Boiling 106
5.3.3 Jet Cooling 109
5.4 Roof Oxygen Tuyeres Increasing the Rate of Scrap Melting 114
5.4.1 Layout of the Tuyeres in the Furnace, Their Design and Basic Parameters 114
5.4.1.1 Calculation 117
Oxygen Flow Rate Vo2 117
Water Flow Rate Per One Tuyere Vw 118
Initial Velocity of Water Jets wo 118
Quantity of Jets n and Pitch of Them x 118
Heat Transfer Coefficient ?w 118
Temperatures of The Tuyere Tip Wall in Danger Zone 119
5.4.2 Controlling Position of Tuyeres at the Slag-Metal Interface 119
References 121
6 Fuel Arc Furnace FAF with Flat Bath: Steel Melting Aggregate of the Future 123
Abstract 123
6.1 Design and Operation 123
6.2 Design Furnace Operation Performances 128
6.2.1 Hourly Productivity 128
6.2.1.1 Determining of Melting Time of Individual Scrap Pieces in FAF 129
6.2.1.2 Determining of Melting Time of the Entire Scrap and Hourly Productivity of FAF 131
6.2.2 Electric and Heat Powers, Consumption of Energy Carriers and Electrodes 132
6.2.2.1 The Scrap Melting Period 132
6.2.2.2 The Metal Heating Period 133
6.2.2.3 Determining the Power of Burner Devices 133
6.2.3 Aerodynamical Parameters of Burner Devices and Shaft 133
6.3 Economy and Environment 134
6.3.1 Economy of Replacement of Electrical Energy with Fuel 134
6.3.2 Environment 136
6.4 Advantages of Fuel Arc Furnaces 137
References 137