Towards a full multi-scale understanding of zero-carbon metal fuel combustion

Project Information

MetalFuel

Grant agreement ID: 884916

DOI

10.3030/884916

Project closed

EC signature date 6 April 2020

Start date 1 October 2020

End date 30 September 2025

Funded under

• EXCELLENT SCIENCE - European Research Council (ERC)

Total cost

€ 2 492 992,50

EU contribution

€ 2 492 992,00

Coordinated by

TECHNISCHE UNIVERSITEIT EINDHOVEN
Netherlands

Periodic Reporting for period 4 - MetalFuel (Towards a full multi-scale understanding of zero-carbon metal fuel combustion)

Reporting period: 2025-04-01 to 2025-09-30

Summary of the context and overall objectives of the project

Energy-on-demand is a cornerstone of modern society. Currently, the primary source of energy is fossil fuel, but in view of undeniable climate warming, alternative fuels are dearly wanted. Metal powders are a tantalizing, totally carbon-free and recyclable option for such a fuel. Its combustion products are solid metal-oxide particles, which, after capture, can be recycled to metal powders again using green electricity. The technology required to burn metal powder aerosols in a stable and reliable way is, however, still in its infancy. Rapid growth of the technology is difficult, because fundamental understanding of combustion of dense metal aerosols is largely lacking. Herein lies a virgin field of fundamental research, with huge potential for practical application. Fundamental principles behind metal fuel flames are addressed in this research, in a step-wise, combined experimental & theoretical/numerical approach. On single-particle level, we unraveled the influence of mutual interactions. Their consecutive ignition will create combustion wave fronts traveling through metal aerosols. Such planar flame fronts will be created in the lab as well as studied numerically and subsequently used as building block for modeling 3D flames. Finally, Bunsen-type burners are developed to characterize turbulent, 3D flames. Detailed experiments using microscopy for metal-(oxide) particle composition as well as new optical diagnostic techniques on dedicated, lab-scale metal aerosol burners served as benchmarks for validation of models. I have a 30 years track record in theoretical, numerical & experimental combustion research, focusing on fundamental aspects of combustion processes relevant to practical applications. In this project this experience has been the foundation from which to explore a new direction in fundamental combustion research. This METALFUEL project will boost to a new branch of combustion research, with the potential for disruptive applications.

Work performed from the beginning of the project to the end of the period covered by the report and main results achieved so far

The ERC MetalFuel project explores how metal powders—especially iron—can be used as a clean, circular energy carrier. Over the course of the project, researchers have made major advances in understanding how metal particles burn, how metal flames behave, and how these processes can be scaled up for real world energy applications. The work spans experiments, modelling, and the development of new diagnostic tools and combustion systems.

Understanding How Individual Metal Particles Burn
Researchers developed new experimental setups to observe single metal particles as they ignite and burn. Using advanced optical techniques, they measured particle size, ignition temperature, combustion time, and temperature history. A new single particle burner and an induction based ignition system were created—one of which is now undergoing patenting.
On the modelling side, detailed and simplified combustion models were built to describe the flow, temperature, and chemical reactions around a burning particle. Molecular level simulations helped improve understanding of how iron and oxygen interact, leading to models that match experiments more closely. These findings have been published and form the foundation for larger scale simulations.

Studying Metal Flames in Controlled Conditions
To investigate how metal powders burn collectively, the team developed new burners capable of stabilizing iron flames. A V shaped burner proved especially effective and allowed researchers to measure flame properties such as burning velocity. Optical diagnostics—including particle tracking and holographic interferometry—were developed to visualize flame structure and temperature fields.
In parallel, numerical models were created to describe one dimensional metal flames. These models capture chemical reactions, phase changes, and the influence of different iron oxides on flame temperature and propagation. A quasi 1D model for stretched flames was also developed and validated. Key results have been published.

Advancing to Full 3D Metal Flames
At the largest scale, the project designed and built a 3D iron particle jet burner in collaboration with Delft University. This system enabled the study of stable, optically accessible metal flames. A new hyperspectral pyrometry technique was developed to measure particle temperatures during combustion, and was validated using single particle experiments. Measurements of temperature fields and flame characteristics in turbulent iron air flames have been published.
On the modelling side, the team implemented advanced metal combustion capabilities into the OpenFOAM simulation platform. These tools were used to study laboratory scale and pilot scale burners, including systems up to 100 kW. The simulations revealed the crucial role of radiative heat transfer in metal aerosol combustion, helping resolve discrepancies between earlier models and experiments. These insights will improve future flame models and have been published.

Overall Impact
The Metal Fuels project has:
• Developed new experimental tools and burners for studying metal combustion
• Created advanced models that describe metal particle and flame behaviour
• Improved understanding of how metal powders burn at scales relevant for energy production

Progress beyond the state of the art and expected potential impact (including the socio-economic impact and the wider societal implications of the project so far)

The ERC MetalFuels project has pushed the boundaries of metal based energy research far beyond existing knowledge, combining fundamental scientific breakthroughs with system level innovations. One of the most significant advances lies in the integration of molecular dynamics (MD) simulations with detailed single particle combustion models. By examining the interaction between partially oxidized iron particles and oxygen molecules at the atomic scale, the project uncovered mechanisms that were previously inaccessible through experiments alone. Collaborations with leading experts, including researchers at Imperial College London, enabled the development of accurate physical property datasets for Fe–O systems. Incorporating these insights into combustion models dramatically improved agreement with experimental observations and revealed the crucial influence of internal particle structure and surface chemisorption on iron oxidation rates—factors that had been underestimated in earlier models. This combined modelling–experimental approach represents a major step forward in predictive metal combustion science.

Beyond particle scale combustion, the project introduced the ICONIC concept, a pioneering approach to metal fuel combustion that relies on the recirculation of hot flue gases, controlled cooling, and re mixing with fresh iron powder and air. This strategy enables stable, efficient, and low emission metal flames under conditions that were previously difficult to achieve. The innovative nature of ICONIC was recognized through the award of an ERC Proof of Concept grant, underscoring its potential to reshape the design of future metal fuel reactors.

Recognizing that metal fuels sit at the intersection of combustion science and metallurgy, the project also invested in material science expertise. Collaborations with renowned institutions in metal oxidation and powder metallurgy helped deepen understanding of particle durability, structural evolution, and performance across repeated oxidation–reduction cycles. These efforts have contributed to raising the technology readiness level of the MetalFuel program and have laid the groundwork for future industrial deployment.

Iron Flame