^ Springer. Innovation in Electric. Arc Furnaces. Ilyaz Y. Zinurov. Scientific Basis for Selection. Yuri N. Toulouevski. Revised and Supplemented

Transcription

1 Yuri N. Toulouevski Ilyaz Y. Zinurov Innovation in Electric Arc Furnaces Scientific Basis for Selection The Second Edition Revised and Supplemented ^ Springer

2 Contents 1 Modem Steelmaking in Electric Arc Furnaces: History and Development General Requirements to Steelmaking Units Process Requirements Economic Requirements Environmental and Health and Safety Requirements High-Power Furnaces: Issues of Power Engineering Increasing Power of EAF Transformers Specifics of Furnace Electrical Circuit Optimum Electrical Mode of the Heat Direct Current Furnaces Problems of Energy Supply The Most Important Energy and Technology Innovations Intensive Use of Oxygen, Carbon and Chemical Heat Foamed Slag Method Furnace Operation with Hot Heel Single Scrap Charging Use of Hot Metal and Reduced Iron Post-Combustion of CO Above the Bath Increase in Capacity of Furnaces Continuous Charging and Melting of Scrap in the Liquid Bath 22 References 24 2 Electric Arc Furnace as Thermoenergetical Unit Thermal Performance of Furnace: Terminology and Designations External and Internal Sources of Thermal Energy: Useful Heat Factors Limiting the Power of External Sources Key Role of Heat Transfer Processes 29 Reference 31 ix

3 x Contents 3 The Fundamental Laws and Calculating Formulae of Heat Transfer Processes Three Ways of Heat Transfer: General Concepts Conduction Heat Transfer Fourier's Law. Flat Uniform Wall. Electrical-Thermal Analogy Coefficient of Thermal Conductivity Multi-Layer Flat Wall Contact Thermal Resistance Uniform Cylindrical Wall Multi-Layer Cylindrical Wall Simplifying of Formulae for Calculation of Cylindrical Walls Bodies of Complex Shape: Concept of Numerical Methods of Calculating Stationary and Non-Stationary Conduction Heat Transfer Convective Heat Exchange Newton's Law: Coefficient of Heat Transfer a Two Modes of Fluid Motion Boundary Layer Free (Natural) Convection Convective Heat Transfer at Forced Motion Heat Transfer Between Two Fluid Flows Through Dividing Wall; Heat Transfer Coefficient k Heat Radiation and Radiant Heat Exchange General Concepts Stefan-Boltzmann Law; Radiation Density; Body Emissivity Heat Radiation of Gases Heat Exchange Between Parallel Surfaces in Transparent Medium: Effect of Screens Heat Exchange Between the Body and Its Envelope: Transparent Medium Heat Exchange Between the Emitting Gas and the Envelope 66 4 Energy (Heat) Balances of Furnace General Concepts Heat Balances of Different Zones of the Furnace Example of Heat Balance in Modern Furnace Analysis of Separate Items of Balance Equations Output Items of Balance Input Items of Balance 75

4 Contents xi 4.5 Chemical Energy Determination Methods Utilization of Material Balance Data About the So-Called "Energy Equivalent" of Oxygen Calculation of Thermal Effects of Chemical Reactions by Method of Total Enthalpies 77 References 82 5 Energy Efficiency Criteria of EAFs Preliminary Considerations Common Energy Efficiency Coefficient of EAF and Its Deficiencies Specific Coefficients rj for Estimation of Energy Efficiency of Separate Energy 5.4 Determining Specific Coefficients r\ Sources and EAF as a Whole Electrical Energy Efficiency Coefficient tjel Fuel Energy Efficiency Coefficient of Oxy-Gas Burners tjng Energy Efficiency Coefficient of Coke Charged Along with Scrap Determining the Specific Coefficients r\ by the Method of Inverse Heat Balances Tasks of Practical Uses of Specific Coefficients t] References Preheating of Scrap by Offgases in Combination with Burners Potentials and Limiting Factors Expediency of Heating Comparison of Consumptions of Useful Heat for Scrap Heating, Scrap Meltdown, and for Heating of Metal up to Tapping Temperature Reduction in Electrical Energy Consumption with High-Temperature Heating of Scrap: Calculation of Potentials Sample of Realization of High-Temperature Heating: Process BBC-Brusa Specifics of Furnace Scrap Hampering Its Heating Heating on Conveyor Consteel Furnaces with Continuous Scrap Charging into the Bath Comparison of Melting Rates, Productivities, and Electrical Energy Consumptions Between the Consteel Furnaces and EAFs Scrap Preheating Temperature 109

5 xjj Contents 6.3 Heating Scrap in a Large-Thickness Layer Ill Heat Transfer Processes Ill Heating Scrap in Baskets and Special Buckets Twin-Shell Furnaces with Removal of Off-Gas Through the Second Bath Heating Scrap in Shaft Furnaces Shaft Furnaces with Fingers Retaining Scrap Shaft Furnaces with Continuous Scrap Charging into the Liquid Bath by Pushers From Utilizing Off-Gases to Scrap Preheating by Burners Only 126 References Replacement of Electric Arcs with High Power Oxy-Gas Burners Attempts for Complete Replacement Potentialities of Existing Burners: Heat Transfer, Limiting Factors High-Power Rotary Burners (HPR-Burners) Fundamental Features Slag Door Burners: Effectiveness of Flame-Direction Changes Roof Burners Oriel Burners Sidewall Burners Two-Stage Process of the Heat with Use of HPR Burners: Industrial Trials General Energy Ratios Process with a Door Burner in 6-ton Furnaces Process with Roof Burners in 100-ton and 200-ton Furnaces Fuel Arc Furnaces (FAFs) FAF with Scrap Heating in a Furnace Freeboard Conveyor FAFs with Continuous Scrap Charging into the Liquid Bath Shaft FAFs with Continuous Scrap Charging by a Pusher Economy of Replacement of Electrical Energy with Fuel 157 References Basic Physical-Chemical Processes in Liquid Bath Blown with Oxygen: Process Mechanisms Interaction of Oxygen Jets with the Bath: General... Concepts Oxidation of Carbon 163

6 Contents xiii 8.3 Melting of Scrap Heating of the Bath Bath Stirring and Splashing During Oxygen Blowing Stirring Intensity: Methods and Results of Measurement Mechanisms of Bath Stirring Stirring Through Circulation and Pulsation Stirring by Oxygen Jets and CO Bubbles Factors Limiting Intensity of Bath Oxygen Blowing in Electric Arc Furnaces Iron Oxidation: Effect of Stirring Bath Splashing Oxygen Jets as a Key to Controlling Processes in the Bath References Jet Streams: Fundamental Laws and Calculation Formulae Jet Momentum Flooded Free Turbulent Jet: Formation Mechanism and Basic Principles Subsonic Jets: Cylindrical and Tapered Nozzles Supersonic Jets and Nozzles: Operation Modes Simplified Formulae for Calculations of High-Velocity Oxygen Jets and Supersonic Nozzles A Limiting Value of Jets' Velocity Long Range of Jets 191 Reference Devices for Blowing of Oxygen and Carbon into the Bath Blowing by Consumable Pipes Submerged into Melt and by Mobile Water-Cooled Tuyeres Manually Operated Blowing Through Consumable Pipes BSE Manipulator Mobile Water-Cooled Tuyeres Jet Modules: Design, Operating Modes, Reliability Increase in Oxygen Jets Long Range: Coherent Jets Effectiveness of Use of Oxygen, Carbon, and Natural Gas in the Modules Blowing by Tuyeres Installed in the Bottom Lining Converter-Type Non-Water-Cooled Tuyeres Tuyeres Cooled by Evaporation of Atomized Water Explosion-Proof Highly Durable Water-Cooled Tuyeres for Deep Blowing 209 References 214

7 xiv Contents 12 Water-Cooled Furnace Elements Preliminary Considerations Thermal Performance of Elements: Basic Laws Principles of Calculation and Design of Water-Cooled Elements Determining of Heat Flux Rates Minimum Necessary Water Flow Rate Critical Zone of the Element Temperature of Water-Cooled Surfaces Temperature of External Surfaces General Diagram of Element Calculation Hydraulic Resistance of Elements Examples of Calculation Analysis of Thermal Performance of Elements Mobile Oxygen Tuyere Elements with Pipes Cast into Copper Body and with Channels Jet Cooling of the Elements Oxygen Tuyere for Deep Blowing of the Bath 235 References Principles of Automation of Heat Control Preliminary Considerations Automated Management Systems Use of Accumulated Information: Static Control Mathematical Simulation as Method of Control Dynamic Control: Use of On-line Data Rational Degree of Automation 249 References Off-Gas Evacuation and Environmental Protection Preliminary Considerations Formation and Characteristics of Dust-Gas Emissions Sources of Emissions Primary and Secondary Emissions Composition, Temperature, and Heat Content of Off-Gases Capturing Emissions: Preparing Emissions for Cleaning in Bag Filters General Description of the System Problems of Toxic Emissions A Simplified Method of Gas Parameters' Calculation in the Direct Evacuation System Energy Problems 268

8 Contents xv 14.4 Use of Air Curtains 270 References 275 Index 277