In-house green hydrogen production for steelmaking decarbonization using steel slag as thermal energy storage material: A life cycle assessment

Abstract

Steel production is a highly energy-intensive industry, responsible for significant greenhouse gas emissions. Electrification of this sector is challenging, making green hydrogen technology a promising alternative. This research performs a thermodynamic analysis of green hydrogen production for steel manufacturing using the direct reduction method. Four solid oxide electrolyzer (SOE) modules replace the traditional reformer to produce 2.88 kg/s of hydrogen gas, serving as a reducing agent for iron pellets to yield 30 kg/s of molten steel. These modules are powered by 37,801 photovoltaic units. Additionally, a thermal storage system utilizing 1342 tons of steel slag stores waste heat from Electric Arc Furnace (EAF) exhaust gases. This stored energy preheats iron scraps charged into the EAF, reducing energy consumption by 5 %. A life cycle assessment, conducted using open LCA software, reveals that the global warming potential (GWP) for the entire process, with a capacity of 30 kg/s, equates to 93 kg of CO2. The study also assesses other environmental impacts such as acidification potential, ozone formation, fine particle formation, and human toxicity. Results indicate that the EAF significantly contributes to global warming and fine particle formation, while the direct reduction process notably impacts ozone formation and acidification potential.