A novel rotary-cavity reactor for sustainable solar metallurgy: Design and experimental demonstration of direct reduction of iron ore

• Direct iron ore reduction with H 2 and solar heat for decarbonized iron/steel making. • A rotary-type solar reactor was designed, constructed and tested for DRI demonstration. • A micrometric powder hastened the kinetics to reach 96% Fe 2 O 3 particle conversion. • Increasing cavity temperature over 1000 °C or H 2 flow rate favored iron production. • Complete ore particles (Ø 1–2 mm) reduction was confirmed by solid products analysis. This study addresses the direct reduction of iron ore with hydrogen and solar energy as the process heat source for clean iron/steel making and decarbonation of the metallurgical process. A novel rotary-type solar reactor was designed, constructed and tested for demonstration of hydrogen-based direct iron ore reduction under real direct solar irradiation. Such a solar reactor concept for clean ironmaking has never been implemented before. The reactor was first simulated to determine the temperature field, gas velocity and H 2 mole fraction contours in the directly-heated cavity for design validation. The on-sun experimental study focused on reactor testing and performance analysis (including Fe products yields and quality). The effect of increasing temperature (>900–1000 °C at the cavity center depending on cavity size) or H 2 flow rate (0.5–1–2 NL/min), and decreasing particle size on promoting the reduction extent was emphasized. Two different cavity designs and materials (stainless steel and mullite) were also considered to show their impact on the process performance. Using a ceramic cavity with smaller diameter allowed reaching higher temperatures over 1000 °C at its center, with faster heating rates and enhanced conversion. High Fe 2 O 3 particle conversion up to 100 % was obtained based on continuous quantification of the H 2 consumed by the reduction reaction. Solid products analysis (XRD, SEM/EDX) confirmed the production of pure Fe by the solar-driven process, therefore offering a promising route toward sustainable solar metallurgy