Advancing hydrogen plasma smelting reduction: Experimental insights from a pilot plant

The hydrogen plasma smelting reduction process is a promising technology for sustainable steel production from iron ores, utilizing molecular, atomic and ionized hydrogen as reducing agents. It is operated in a gas-tight direct-current electric arc furnace with a hollow graphite cathode for material and gas feeding. To investigate scale-up parameters, a pilot plant with a capacity of 100 kg of iron ore per trial has been built at the site of voestalpine Stahl Donawitz GmbH in Leoben, Austria, and is operated by K1-MET GmbH, Linz, Austria. This study describes the pilot setup in detail and examines the impact of selected parameters on the reduction process. Therefore, thermal insulation is applied to the vessel to mitigate heat losses and enable higher bath temperatures. Furthermore, different crucible refractory materials are evaluated for their wear characteristics. Additionally, varying input materials, including pre-reduced ore, are processed and their influence on the reduction kinetics is discussed. It is observed, that the gangue content significantly affects the reduction process. Thermally insulating the vessel leads to better separation of the slag and metal phases as well as lower energy consumption. The refractory wear is reduced by using phosphate-bonded magnesia lining. These combined results provide insights into the optimization of process conditions for hydrogen plasma smelting reduction at pilot scale.