1 General Introduction 1.1 Electric arc furnace steelmaking 1.1.1 Introduction of EAF steelmaking 1.1.2 General situation of EAF steelmaking development at home and abroad 1.2 Research on injection technology of EAF steelmaking 1.2.1 Oxygen injection technology 1.2.2 Oxygen burner technology 1.2.3 Coherent jet technology 1.2.4 Bottom blowing mixing technology 1.2.5 Carbon powder injection technology to produce foam slag 1.3 Research on gas-solid injection smelting technologyin steelmaking process 1.3.1 Gas-solid injection smelting technology outside the molten bath 1.3.2 Gas-solid injection smelting technology in the molten bath 1.4 New technology of submerged gas-solid injection smelting in EAF steelmaking 1.4.1 Advantages of the new process of submerged gas-solid injection 1.4.2 Key technical issues to be solved in the new technology 2 Mechanism of EAF Steelmaking with Submerged MixedInjection 2.1 Dephosphorization Mechanism by Lime Powder Injectionin the molten bath 2.1.1 Principle of dephosphorization by lime powder injection 2.1.2 Comparison of dephosphorization effect of lime powder injection 2.2 Mechanism of carbon powder injection inthe molten bath 2.2.1 Analysis of scrap melting process 2.2.2 The influence of the carbon content in the molten bath on the meltingrate of scrap 2.2.3 The influence of molten bath fluid flow on the melting rate of scrap 2.3 Material and energy analysis of submerged gas-solidinjection smelting in EAF 2.3.1 Raw and auxiliary materials conditions 2.3.2 Assumptions 2.3.3 Establishment of material balance model 2.3.4 Establishment of heat change model 2.3.5 Material and heat balance calculation results 2.3.6 Analysis of the influence of gas-solid injection parameters onmaterials and heat 2.4 Chapter summary 3 Impact Characteristics of Submerged Gas Injection 3.1 Characteristics of gas injection and gas-solidinjection 3.1.1 Mathematical modeling of submerged gas-solid injection jet trajectory 3.1.2 Analysis of gas jet trajectory 3.1.3 Analysis of submerged gas-solid injection jet trajectory 3.2Hydraulic simulation study of submerged gas-solid injection in the molten bath 3.2.1 Experimental device and method 3.2.2 Experimental program 3.2.3 Experimental results and analysis 3.3 Numerical simulation study of submerged gas-solid injection 3.3.1 Numerical simulation scheme 3.3.2 Governing equation 3.3.3 Model establishment 3.3.4 Analysis of numerical simulation results 3.4 Chapter summary 4 Impact Characteristicsof Coherent supersonic jet 4.1 Numerical simulation 4.1.1 Assumptions 4.1.2 Numericalmodeling and validation 4.1.3 Analysis of numerical simulation results 4.2 Water model experiment 4.2.1 Water model experiment platform 4.2.2 Experimental program 4.2.3 Experimental results and analysis 4.3 Coupled calculation model of oxygen jet impingingmolten bath 4.3.1 Coupled calculation modeling 4.3.2 Model correction and error analysis 4.4 Chapter summary 5 Fluid flowcharacteristics of EAF with Submerged Mixed injection 5.1 Water model experiment EAF molten bath with ofsubmerged injection 5.1.1 Experimental parameters are determined 5.1.2 Experimental schemes and methods 5.1.3 Analysis of experimental results 5.2 Water model experiment of EAF molten bath with submergedinjection and coherent jet 5.2.1 Parameter determination 5.2.2 Experimental schemes and methods 5.2.3 Analysis of experimental results 5.3 Numerical simulation of EAF molten bath with submerged injection and coherentjet 5.3.1 Simulation scheme 5.3.2 Model establishment 5.3.3 Analysis of numerical simulation results 5.4 Chapter summary 6Industrial test research 6.1 Industrial test research on submerged oxygeninjection 6.1.1 Test plan 6.1.2 Test results and analysis 6.1.3 Summary 6.2 Industrial test research on submerged carbon powderinjection 6.2.1 Test plan 6.2.2 Test results and analysis 6.2.3 Summary 6.3Chapter summary 7 Conclusions