Hydrogen-resistant refractories for direct reduced iron production

In the steelmaking industry, the largest share of CO2 emissions comes from the reduction of iron ore. A switch from the blast furnace (BF) / basic oxygen furnace (BOF) route to the direct reduced iron (DRI) process with natural gas followed by the electric arc furnace (EAF) already enables CO2 savings of up to 38%. However, in order to meet the mid- to long-term CO2 targets of the iron and steel industry, further measures are required. Most DRI plants are currently operating on natural gas, which results in approximately 60% hydrogen in the process gas. However, currently projects are underway to determine if DRI units can operate at hydrogen levels at or close to 100%, which could further reduce CO2 emissions by more than 80%. In this context, it is important to consider the impact of hydrogen on the refractory lining in the DRI shaft kiln. Previous studies have shown that hydrogen can permeate through refractories and reduce ceramic oxides under certain process conditions. Silica-containing materials are reported to be especially susceptible to hydrogen attack. However, a deeper understanding of corrosion mechanisms is still needed. This article presents the first results of experimental work carried out by RHI Magnesita on the impact of hydrogen on refractory systems. Investigations were conducted on the effect of hydrogen exposure on the composition and microstructure of refractory bricks. This enables refractories to be identified that are suitable for lining a DRI shaft kiln where hydrogen is used as a reductant and will support the development of novel hydrogen-resistant refractory solutions