Project in the Spotlight: CHIRON: Towards a Carbon-Lean HIsarna® Ironmaking Process

Project Description

Key information
Project in the Spotlight: T20009
Market: Advanced Metals

Written M2i Program Manager: Viktoria Savran

Steel production is one of the world’s most energy-intensive industries, and reducing its carbon footprint is a pressing global challenge. The CHIRON project, “Towards a carbon-lean HIsarna® ironmaking process”, tackles this issue by exploring how hydrogen can be used to reduce iron ore in place of coal within Tata Steel’s innovative HIsarna process. The research focuses on understanding whether hydrogen can lower carbon emissions while maintaining the process efficiency and product quality that modern steelmaking demands.

For TU Delft researcher Philipp Leerhoff, working under the supervision of Prof. Yongxiang Yang, supported by Prof. Shoshan Abrahami and Prof. Neslihan Dogan of the MPRR group, and in close collaboration with Tata Steel, that question became both scientific challenge and industrial need. Supported by Top Sector High Tech Systems and Materials (HTSM) via PPS funding, the project digs deep into how hydrogen enrichment, ore mineralogy and microstructure affect the smelting reduction of fine iron ores within the HIsarna furnace—a breakthrough technology developed by Tata Steel in IJmuiden.

Advancing HIsarna® Toward Hydrogen Readiness

Blast furnace ironmaking is energy intensive and therefore the CO₂ footprint is high. The HIsarna process achieves up to 20% CO₂ emission reduction by eliminating the need for coking and sintering, and directly smelting fine iron ores with coal. Over 90 % emission reduction can be gained through carbon capture, and negative CO₂ emissions are achieved when also renewable biochar is used. The CHIRON project builds on this innovation by introducing hydrogen as an additional reducing agent—paving the way toward a truly carbon-lean process.

In HIsarna, fine ore particles are injected into a smelt cyclone, where they are rapidly melted and partially reduced by the ascending gases from the smelting reduction vessel (SRV) below. The challenge lies in understanding how hydrogen interacts with these fast-moving particles under extreme temperatures (up to 1500 °C), and how it influences the overall reaction kinetics, heat balance, and final metal quality.

“Transitioning from carbon to hydrogen in ironmaking is not a simple substitution,” explains Prof. Yang. “Hydrogen reduction is endothermic—it absorbs heat—so we need to carefully balance the energy and chemical reactions in the furnace to maintain process stability and product quality.”

Science behind the steel
To explore these effects, Leerhoff designed a series of high-temperature experiments using both, a drop-tube furnace and thermogravimetric analysis at TU Delft’s Department of Materials Science and Engineering. In these setups, fine ore particles are suspended in a controlled reducing atmosphere containing varying proportions of H₂, CO, CO₂, and H₂O—mirroring the complex gas composition of the HIsarna cyclone.

His experiments revealed a clear trend: increasing hydrogen levels accelerate the reduction process, particularly the conversion of magnetite (Fe₃O₄) to wustite (FeO). However, due to the presence of H₂ and CO₂ at these high process temperatures up to 1500 °C, the water-gas shift reaction can have a major impact on the reduction atmosphere, limiting the positive influence of H₂. At the same time, the nature of the ore proved equally critical. Goethite-rich ores, abundant in regions like India, showed higher reactivity and achieved greater conversion than purely hematite ores. These findings highlight the importance of matching ore mineralogy to hydrogen-enriched environments to achieve optimal performance.

Microscopic analysis further confirmed that at high temperatures, diffusion of the reducing gas through the developing product layer becomes the rate-determining mechanism—an insight that helps refine the kinetic models used by Tata Steel to simulate and optimize the HIsarna process. In practical terms, this means better predictions of ore behavior, reduced reliance on carbonaceous fuels, and a shorter path to scale-up.

From laboratory to industry
For Tata Steel, the industrial implications are significant. By partially replacing coal with hydrogen, it is possible to lower CO₂ emissions from ironmaking—a critical step toward its 2050 vision of carbon-neutral steel production. The kinetic models and reduction data generated in CHIRON are now being integrated into Tata Steel’s computational models of the HIsarna process, supporting the design of future demonstration and industrial-scale plants.

Christiaan Zeilstra: “Projects like CHIRON bridge the gap between academic insight and industrial application. They allow us to fine-tune groundbreaking processes like HIsarna, ensuring that sustainability goals translate into operational reality.”

The human element
For Philipp, the experience was transformative. “Working at the intersection of materials science and sustainable industry was incredibly rewarding. Seeing how our experimental results feed directly into Tata Steel’s models and process improvements makes the research feel tangible and impactful.”

And for M2i, the CHIRON project exemplifies what the institute stands for: connecting academic research with real-world industrial innovation. CHIRON is a perfect example of how collaborative R&D accelerates the transition to a low-carbon economy. The knowledge developed here will provide alternative technologies and help shape the next generation of sustainable steelmaking.”

Looking ahead
The CHIRON project does not end at the laboratory scale. The insights gained are feeding directly into Tata Steel’s pilot and future demonstration plants, helping design a process that minimizes fossil fuel dependence while maintaining high-quality steel output. Future research will continue to refine the kinetic models, explore alternative ore compositions, and extend the hydrogen-assisted smelting approach toward other process steps.

As global industry looks for viable routes to decarbonization, CHIRON stands as a reminder that meaningful change happens where science meets steel—and collaboration meets courage.