Establishing Stanford’s place in the carbon-zero steelmaking economy

Team: Leora Dresselhaus-Marais, Alexander Dudchenko, Subhechchha Paul, Xueli Zheng
Planning (Scoping)

Steel is ubiquitous in society because its mechanical and thermal properties offer high performance and tunability. In 2020, industry produced 1.86 billion tons of steel, and demand is growing exponentially. Today’s steelmaking accounts for 8% of annual global CO2 emissions; it emits ~1.85 kilograms of CO2 per kilogram of steel. This project seeks a fast path to decarbonize industrial steelmaking. 

The primary carbon footprint in steelmaking originates from ironmaking, which reduces natural iron oxides (ores) into metallic iron for subsequent alloying and processing. A conventional blast furnace, a 100-meter tower with temperatures near 1800 C, reduces iron ores – e.g., hematite (Fe2O3) and magnetite (Fe3O4) – with the aid of processed coal (i.e., coke, or carbon). It relies on limestone (CaCO3) to remove impurities (gangue) and precipitate them into slag. To decarbonize ironmaking, direct iron reduction (DIR) employs smaller shaft furnaces whose gas-phase reagents eliminate the need for coal. DIR furnaces operate at lower temperatures (600-900 C), significantly reducing the energy demands. However, they introduce challenges such as process scaling inefficiencies, purity requirements for incoming iron ore, and the use of grey hydrogen as a reducing agent. 

The researchers are studying the fundamental chemistry and mechanical transformations in H2-only ironmaking to elucidate the chemical mechanisms at the atomic scale and to integrate the fundamental science with process-scale models. The goal is to optimize hydrogen-based DIR with the aid of techno-economic models. The project team has engaged with several traditional and innovative steel industry partners, and these collaborations have led to the level of $825,000 of funding from the U.S. Department of Energy over five years.