Abstract
The HAlMan project (Hydrogen, Aluminum and Manganese) is a Horizon Europe-funded initiative aimed at revolutionizing the metallurgical industry by developing a carbon-free, zero-waste route for manganese and ferromanganese alloy production. Traditional methods rely on carbothermic reduction in submerged arc furnaces, which are energy-intensive and contribute significantly to global CO2 emissions. The HAlMan process replaces fossil carbon with hydrogen for the initial prereduction of manganese ores to MnO and subsequently uses secondary aluminum (such as scrap or dross) as a reductant for final smelting. This integrated approach not only targets a large reduction in CO2 emissions but also valorizes industrial byproducts, creating a sustainable circular economy within the ferroalloy sector.
This study presents the results of three pilot-scale hydrogen prereduction campaigns conducted at SINTEF’s facilities in Trondheim, Norway, using Nchwaning manganese ore. Utilizing a 300 kW graphite plasma rotary furnace, approximately 1.5 tonnes of ore were processed to produce feedstock for subsequent aluminothermic smelting at MINTEK.
The results demonstrate that the degree of reduction is primarily driven by residence time at reaction temperature rather than the total quantity of hydrogen supplied with a highest achieved reduction yielding a 20% weight loss. Analysis via XRD and EPMA confirmed the successful conversion of higher manganese oxides to MnO and the partial formation of metallic iron. It was determined that 163% of the stoichiometric hydrogen requirement (~1.6x the theoretical amount) was sufficient for effective prereduction under these pilot conditions. These findings validate the scalability of the HAlMan prereduction stage and provide critical operational parameters for future industrial-scale fossil-free manganese production.