Short Process Electric Arc Furnace (Short Process EAF): Integration of Melting and In-Furnace Refining – Process Features and Technical Advantages

Short Process Electric Arc Furnace (Short Process EAF): Integration of Melting and In-Furnace Refining – Process Features and Technical Advantages

1. Introduction

The Short Process Electric Arc Furnace (Short Process EAF) represents a significant innovation in modern steelmaking, distinguished by its highly integrated melting and in-furnace refining process. Unlike traditional long-process EAFs, which separate melting and refining steps, the short process EAF simultaneously melts scrap steel and performs in-furnace refining operations. This approach reduces the residence time of molten steel, improves production efficiency, minimises energy consumption, and ensures uniform chemical composition and temperature distribution—a critical requirement for high-quality steel production.

This article provides an in-depth analysis of the process features, technical principles, operational mechanisms, and integrated advantages of melting and in-furnace refining in short process EAFs.

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2. Process Principles of Short Process EAF

The core of the short process EAF lies in the synchronous execution of scrap melting and molten steel refining within a single furnace. The process can be summarised in three essential stages:

1. Rapid Scrap Melting: High-density electric arcs quickly melt scrap steel, generating the heat necessary for subsequent refining.

2. In-Furnace Refining Integration: Oxygen injection, carbon injection, alloy addition, and slag control occur concurrently with melting, enabling decarburization, desulfurization, alloying, and slag formation in real time.

3. Thermal and Chemical Control Optimisation: Slag layer protection and precise temperature control maintain uniform steel temperatures and chemical composition, minimising secondary alloy consumption and refractory wear.

The fundamental advantage of this process is the integration of melting and refining, which shortens the steelmaking cycle, reduces energy consumption, and enhances molten steel quality.

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3. Characteristics of the Melting Stage

3.1 High-Power Arc Melting

Short process EAFs typically employ high-power-density electrical systems. Electrodes generate arcs via alternating or direct current to rapidly melt scrap steel:

• Arc Temperature: 3000–3500°C, capable of melting scrap efficiently.

• Arc Density Control: Optimised electrode positioning and power settings ensure uniform furnace temperature, avoiding localised overheating.

• Rapid Melting: The melting cycle is significantly reduced, typically 20–40% shorter than conventional long-process EAFs.

3.2 Scrap Preheating and Charging Optimisation

• Scrap Preheating: Utilising top-gas waste heat or external heat recovery systems to preheat scrap to 200–400°C reduces the energy required for arc melting.

• Charge Ratio Optimisation: Adjusting the proportions of scrap, direct reduced iron (DRI), or pig iron, and adding fluxing agents, ensures optimal conditions for in-furnace refining.

• Layered Charging: Stratified charging improves heat distribution and promotes uniform slag formation.

3.3 Dynamic Control of Scrap Melting

• Real-time monitoring of electrical current, voltage, and furnace temperature coordinates melting rates with refining operations.

• Efficient arc control minimises refractory wear while maintaining uniform steel temperature.

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4. Characteristics of In-Furnace Refining Integration

In the short process EAF, in-furnace refining is fully integrated with melting, encompassing oxygen injection, carbon and alloy addition, and slag management.

4.1 Oxygen Injection

• Purpose: Decarburization, desulfurization, slag formation, and impurity removal.

• Method: Multi-point oxygen injection, with controlled flow rates and angles, ensures rapid reactions in the molten steel.

• Effect: Achieves target chemical composition quickly, maintaining uniform and stable temperatures.

4.2 Carbon and Alloy Injection

• Carbon Injection: Adjusts carbon content during refining to reach precise steel specifications.

• Alloy Addition: Rapid in-furnace alloying enhances the production of high-end or low-alloy steels.

• Precision Control: Real-time chemical composition monitoring enables accurate dosing, reducing secondary alloy consumption.

4.3 Slag Control

• Composition: Optimised fluxes such as lime, magnesia, and silicates facilitate desulfurization and protect the molten steel surface.

• Dynamic Management: Real-time monitoring of slag thickness and flow maintains thermal efficiency and minimises refractory wear.

• Thermal Efficiency: A stable slag layer reduces heat loss and improves overall energy utilisation.

4.4 Synchronized Melting-Refining Optimization

• Process Coordination: Melting rates are coordinated with refining operations to avoid excessive steel residence time.

• Steel Quality Enhancement: Ensures uniform temperature and chemical composition.

• Production Efficiency: Shortens overall steelmaking cycles and accelerates tapping.

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5. Process Control and Real-Time Optimisation

Short process EAFs rely on precise process control for effective integration:

1. Temperature and Power Control: Arc power is adjusted according to scrap melting rate and molten steel temperature.

2. Chemical Composition Monitoring: Sensors and online analysers monitor carbon, sulfur, phosphorus, and other elements, guiding precise alloy additions.

3. Slag Layer Management: Continuous monitoring of slag thickness and composition optimises thermal protection.

4. Automation and Intelligence: Data acquisition, AI algorithms, and digital twins dynamically optimise melting-refining operations.

This real-time control ensures synchronised melting and refining, the cornerstone of short process EAF efficiency.

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6. Technical Advantages

6.1 High Efficiency

• Integrated melting and refining reduce the steelmaking cycle by 20–40%.

• Shorter tapping times increase furnace throughput and production efficiency.

6.2 Energy Savings

• Scrap preheating and in-furnace refining integration reduces electricity consumption per ton of steel by 10–15%.

• Improved thermal efficiency decreases the need for secondary heating.

6.3 High-Quality Steel

• Synchronised refining maintains uniform temperature and chemical composition.

• Precise alloy addition reduces secondary alloy waste.

• Suitable for producing high-end and low-alloy steels with consistent quality.

6.4 Environmental Benefits

• Lower carbon emissions compared with traditional EAFs.

• Higher scrap utilisation reduces raw material consumption.

• Waste heat and slag recycling enhance energy efficiency and reduce environmental impact.

6.5 Flexibility and Intelligence

• Automation enables real-time optimisation of melting-refining processes.

• Data analysis and digital twins support predictive maintenance and process improvement.

• Process flexibility accommodates different steel grades and feedstock variations.

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7. Conclusion

The integration of melting and in-furnace refining in short process EAFs allows for rapid steel melting, efficient refining, reduced energy consumption, and high-quality steel production. Key advantages include:

• High Efficiency: Shorter steelmaking cycles and higher furnace throughput.

• Energy Savings: Lower electricity consumption and improved thermal efficiency.

• High Steel Quality: Uniform temperature and chemical composition suitable for high-end steels.

• Low Carbon and Green Production: Reduced carbon footprint and high scrap utilisation.

• Intelligent Operations: Automated and data-driven process control ensures stable and optimised production.

The integrated melting-refining process is the core technological feature of short process EAFs, providing modern steel plants with a highly efficient, green, and intelligent solution for high-quality steel production.