Sustainable production of battery-grade nickel via hydrogen reduction of saprolite

Abstract

Abstract Nickel production from saprolite—a major laterite source—is critical for the electric vehicle battery supply chain but is currently constrained by the high carbon footprint of the conventional Rotary Kiln-Electric Furnace (RKEF) process. Hydrogen-based reduction offers a sustainable alternative; however, optimizing the reaction kinetics and phase separation efficiency remains a challenge for industrial application. In this study, we investigated the hydrogen reduction behavior of saprolite ore using a dynamic reduction system to maximize Nickel Pig Iron (NPI) recovery. The effects of reduction time, temperature, gas flow rate, and particle size were systematically evaluated. The results revealed that particle size is the governing factor overcoming the diffusion resistance within the Mg-rich silicate matrix. Optimal reduction efficiency (~ 20 wt% mass loss) was achieved rapidly within 15 min at 900 °C with a particle size of -45 μm. Furthermore, a high-grade NPI (Fe ~ 73 wt%, Ni ~ 25 wt%) was successfully produced with a clear separation from the silicate slag phase. These findings demonstrate that controlling physical parameters based on mineralogical constraints is key to enhancing the reduction efficiency of hydrogen reduction, providing a viable pathway for low-carbon nickel smelting processes.