Three key factors for EAF productivity in green steel hybrid melt shops
The complex dynamics of EAF productivity play a pivotal role in achieving the strategic objectives of a hybrid melt shop. Three factors determine whether you reach your production target.
1. Number of EAFs and EAF design
In most cases, the new EAF should match the productivity of the BOF, since the entire melt shop is adapted to its pace. However, the decision often comes down to choosing between one highly powerful EAF or two EAFs with a slower speed.
This choice significantly impacts:
- Space requirements and CAPEX
- Crane utilization and ladle traffic
- Overall melt shop operations
Factors such as transformer rating (which affects melting time) and vessel geometry (hot heel capacity, scrap capacity) contribute to varying tap-to-tap times for different steel grades and raw material scenarios.
2. Availability of charge materials and energy
During the initial phase of the hybrid melt shop, there is typically an excess of hot metal available. This surplus proves beneficial when charged to the EAF, as it reduces tap-to-tap time and minimizes trace elements. Proper sequence planning for EAF and BOF is crucial to coordinate the hot metal buffer effectively.
In a later stage, a DRI module might be installed allowing hot DRI charging, gradually phasing out hot metal. Any varying feeding rate of hot DRI must be carefully balanced with buffered cold DRI or scrap, introducing new factors that affect the final tap-to-tap time.
The production rate is further influenced by the availability of energy. External power restrictions or internal economic considerations may result in reduced power input, leading to longer tap-to-tap times.
3. Steel grade requirements
At the heat level, the tap-to-tap time depends on the chemical requirements of the steel grades. For grades with specific requirements, a targeted charging mix is designed.
High scrap rates at low-volume EAFs can lead to two-bucket charging, reducing productivity. Similarly, steel grades demanding the lowest trace element levels may require a high HBI charge mix, further decreasing throughput. This is why productivity can shift abruptly between tundish changes or from one heat to another.
Why this matters
These three factors interact dynamically and cannot be evaluated in isolation. A comprehensive simulation that accounts for all variables — across different production scenarios and steel grade mixes — is the only way to quantify the true productivity of your future hybrid melt shop.