Benchmarking of FeNi Electric Arc Furnace Operations for Developing Furnace Design Parameters for Lateritic Ores in the Intermediate SiO2/MgO Range of between 2.2 and 2.7

An extensive benchmarking study was conducted to establish the design for a circular 3-electrode electric furnace of 55MW for smelting of nickel saprolitic laterite ores in the intermediate SiO2/MgO range of 2.2-2.7. The investigation was focused on “intermediate slags” in the compositional range of 15-25% FeO, 0-5% Al2O3 and a SiO2/MgO ratio of 2.2-2.7. Industrial furnace references, operating at SiO2/MgO ratios of <2.2 and >2.7, were reviewed as basis for the design. It was found that slag superheats of up to 200°C is needed when producing high grade ferronickel. The bath resistance was estimated to 9-18mOhm and the operational resistance at shielded arc conditions to 35-55mOhm (Parc/Pbath ratios of 2.0-3.0), corresponding to a secondary voltage in the range of 1400-1750V. From the risk mitigation point of view due to slag characteristics, the furnace design was not limited to operation in shielded arc mode solely, but also towards brush arc operation. At the selected hearth power density of ~200 kW/m2 a wide operation window (Parc/Pbath ratio 1.0-2.6) was found manageable to realize freeze lining control at the estimated peak sidewall heat flux of maximum 165kW/m2. A fit for purpose conservative design approach was defined, aligned with industrial references as well as the latest furnace technology developments in intensive copper cooling elements and power stabilization system, which provides a sound basis for the proposed approach.