A Study on Burning Iron Particles as Carbon-Free Circular Fuels with co-Generation of Value-Added Nanomaterials

NON-TECHNICAL SUMMARY

Energy transition from fossil fuels to renewables is necessary to mitigate climate change and, thereby, advance the national health, prosperity and welfare. However, renewable energy, mostly solar or wind, is not always available at the location or the time when demand is high (e.g., in high earth latitudes, winter months, evenings). Hence, a cost-competitive and effective renewable energy carrier must be able to store available energy and transport energy to be used where and when it is needed.

This would enable storage and/or transportation of renewable energy over long distances. Surprisingly to most people, a promising energy carrier candidate is iron powder. The iron fuel cycle could offer an abundant green energy source and storage methodology to help meet the world’s growing energy needs.

Submillimeter sized iron powder can be manufactured from scrap metal with existing industrial techniques, it can be transported to either existing or dedicated electric utility or industrial furnaces, where it can be ignited and burned like pulverized coal. During combustion, these iron particles generate iron oxide particles of sizes similar to the input iron particles.

The energy emitted during combustion (heat) can be used to generate steam which, thereafter, can spin a steam turbine and generate electricity. Spent iron oxide particles can be reduced back to iron, using green hydrogen and energy, both of which can be obtained from solar panels or wind turbines. This research is advancing the science of powdered iron as a “circular fuel” and is fully characterizing the products and any generated byproducts (such as nanosized oxide particles) while also identifying appropriate applications for the latter materials, such as in supercapacitors, lithium battery anodes, catalysts, environmental cleanup agents as well as materials for medical imaging, targeting, drug delivery, and biosensing.

This research is educating graduate and undergraduate students in the benefits and challenges of sustainable energy harvesting and storage, as well as combustion generated materials. TECHNICAL SUMMARY

Iron is a compelling candidate for a carbon-free circular fuel due to its abundance, high energy density, and strong ability to store and transport energy. Iron can be ignited and burned at elevated temperatures (>2000 K) and, thus, it can be a direct replacement for coal in coal-fired boilers. By leveraging existing infrastructure for carbon-free power generation, iron fuel can be transformative to the utility industry.

It generates zero emissions of carbon dioxide (CO2), zero emissions of sulfur dioxide (SO2), zero emissions of unburned hydrocarbons HC) and ultra-low emissions of nitrous oxide (NOx). Currently, the iron fuel cycle has incomplete scientific understanding and results in the generation of some nanomaterial byproducts, typically considered a waste stream.

Instead, it is hypothesized that these iron-based nanomaterials can yield high-value products. The proposed research is generating fundamental understanding of the physical transformations that occur during the burning of iron particles and the conditions that produce value-added iron-based nanomaterials. The goal of the project is to determine process-structure-property relationships in two distinct streams of use-inspired products: submillimeter-sized oxide particles that can be recycled back to iron, and nano-sized particles with considerable monodispersity and tailorable properties.

Success is being assessed by generating a comprehensive data set on thoroughly-measured iron combustion parameters, fully characterizing the produced nanoparticles and completing an energy/exergy analysis to identify irreversibilities within the fuel cycle.

This award reflects NSF's statutory mission and has been deemed worthy of support through evaluation using the Foundation's intellectual merit and broader impacts review criteria.