Scrap preheating refers to the process of heating steel scrap before it enters the electric arc furnace for melting. By utilizing various heat sources—especially waste heat from the furnace itself—scrap can be raised to a certain temperature prior to melting. This technique is increasingly adopted to reduce energy consumption, shorten melting cycles, and optimize overall steelmaking efficiency.
Why Preheat Scrap?
Traditional EAF operations emit large volumes of off-gas, with temperatures ranging from 1200°C to 1500°C. Without recovery, this high-temperature gas escapes into the atmosphere, carrying away approximately 15% to 20% of the total thermal energy—equivalent to an energy loss of 80–120 kWh per ton of steel.
Scrap preheating systems capture this waste heat to elevate the scrap temperature before it enters the furnace. As a result, power consumption is significantly reduced and overall energy efficiency is improved.
Key Advantages of Scrap Preheating
- Reduced Energy Consumption: Energy savings range from 13.5% to 20%, translating to 50–100 kWh per ton of steel.
- Lower Electrode Consumption: Consumption is reduced by approximately 20% (0.15–0.3 kg per ton).
- Less Dust Generation: Dust emissions can drop by around 30%, improving the working environment and lowering filtration costs.
- Cost Reduction: Overall production costs may decrease by 15%–21%.
- Shorter Melting Time: Preheated scrap melts faster, reducing cycle times by about 20%.
- Increased Output: Production capacity may increase by 10%–20%.
- Higher Efficiency with Double-Shell EAFs: Power utilization can reach up to 83%, outperforming standard single-shell EAFs.
Environmental Challenges and Concerns
Despite its benefits, scrap preheating also presents environmental challenges. Certain preheating technologies may emit harmful substances such as dioxins, furans, sulfides, and chlorides during the heating process. Without effective treatment, these pollutants can pose serious risks to air quality and public health.
In countries with strict environmental regulations—particularly in Europe—scrap preheating is discouraged or tightly controlled. Instead, advanced off-gas cooling systems and post-combustion technologies are preferred to minimize harmful emissions while still recovering some heat.
