Impact of Direct Reduced Iron (DRI) on Electric Arc Furnace Steelmaking

Impact of Direct Reduced Iron (DRI) on Electric Arc Furnace Steelmaking

1. Productivity and Yield  

Production experience shows that using DRI significantly affects the productivity and yield of electric arc furnaces. In China, many recently commissioned large EAF plants face challenges due to poor scrap quality, with bulk densities as low as 0.3–0.7 t/m³. This often requires 3–4 scrap charges per heat. By replacing low‑density scrap with DRI, the number of charges can be reduced, shortening the melting cycle. Continuous addition of 20–50% DRI can substantially increase furnace productivity, especially when combined with oxy‑fuel burners, foamed slag practice, and scrap preheating.

Steel yield is influenced by the metallization degree, gangue content, and carbon level of the DRI. Higher metallization rates promote better recovery, and carburizers may be added to enhance iron reduction. Slag properties and volume also affect yield; for example, foamed slag at constant basicity can lower slag volume, thereby improving yield.

2. Consumption of Production Materials  

- Electrode Consumption: DRI generally contains little carbon. Additions often require carburizers, which create a reducing atmosphere that reduces electrode oxidation. Although submerged‑arc foaming slag practice can raise arc concentration and increase the risk of electrode breakage, overall electrode consumption typically does not increase with DRI use.  

- Refractory Consumption: Batch‑charging DRI does not significantly increase refractory wear. However, continuous charging may cause “slag splashing” and arc exposure, leading to slightly higher refractory attack. Higher FeO in slag and prolonged C–O reaction times can also intensify chemical erosion, but proper foaming slag control and process adjustments can maintain refractory life at original levels.  

- Flux Consumption: DRI introduces acidic gangue, which would normally require more flux to maintain slag basicity. Studies indicate that each 1% increase in DRI usage raises flux demand by about 1 kg/t. However, because DRI contains low phosphorus and sulfur, lower slag basicity may be acceptable, offsetting the increase in flux consumption.

3. Changes in Energy Consumption  

Energy consumption generally rises when DRI is used, due to:  

- Endothermic Reduction of FeO: The lower the metallization rate, the higher the FeO content. Reducing 1 ton of FeO consumes approximately 800 kWh of electrical energy.  

- Gangue Content: Higher SiO₂ requires more quicklime to maintain basicity, increasing slag volume. Melting 1 ton of slag consumes about 530 kWh.  

- Carbon Content: DRI with higher carbon can reduce power demand because the reaction [C] + [O] → CO is exothermic. Each additional Nm³ of oxygen blown can lower electricity use by 2–4 kWh.  

- Charging Method: Continuous charging at optimized rates (28–38 kg/MW·min for cold DRI; up to 50 kg/MW·min for hot DRI) allows full‑power operation, shortening heat time. Batch charging, especially if DRI piles near walls, can prolong melting and raise energy use.  

- Charge Temperature: Fully cold DRI can increase power consumption by 100–150 kWh/t compared to all‑scrap melting, whereas hot‑charged DRI approaches scrap‑only energy levels.

To minimize energy use, high‑metallization DRI with low SiO₂ is recommended, along with appropriate carburization, hot charging, and continuous feeding. Preheating DRI can also help, though precautions against re‑oxidation are necessary.

4. Steel Quality  

Globally, DRI is widely used to produce high‑quality steels in EAFs, including:  

- Oil‑country tubular goods (casing, drill pipe)  

- Deep‑drawing automotive sheet  

- Special‑purpose wires and steels (spring steel, bearing steel)  

- Rotor steels, gun‑barrel steels, and materials for aerospace, aviation, and nuclear applications  

Because DRI contains negligible residual elements (Cu, Ni, Cr, Mo, etc.), it enables production of cleaner steels with fewer inclusions, improving hot‑ and cold‑rolling performance—especially tensile properties. DRI also helps lower sulfur content and modify sulfide inclusion morphology, enhancing steel quality, ductility, and resistance to expansion and torsion.

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