Reducing Iron Oxides without Carbon by using Hydrogen-Plasma

Introduction

With 1.8 billion tons produced per year, steel is the dominant metallic material. It can be recycled by melting scrap, a resource satisfying at most 30% of the demand. Hence, fresh steel must be produced in huge amounts, from oxide minerals reduced by CO in blast furnaces, followed by partial removal of C by O2 in converters.

Environmental Impact

These two processes create ~2.1 tons CO2 per ton of steel, qualifying steelmaking as the largest single greenhouse gas emitter on earth (~8% of all emissions). ROC tackles the fundamental science needed to drastically cut these staggering CO2 numbers, by up to 80% and beyond. This is the biggest single leverage we have to fight global warming.

Disruptive Approach

The disruptive approach of ROC lies in:

1. Using H instead of C as reductant.
2. Merging the multiple steps explained above into a single melting plus reduction process which can run with green electricity, namely, an electric arc furnace operated with a H-containing reducing plasma.

ROC’s approach is feasible as it can be upscaled by modifying existing furnace technology. The motivation is that solid Fe from other synthesis methods such as direct reduction must anyway be melted after reduction.

Hybrid Processes

Project ROC also addresses hybrid processes, where partially reduced oxides from direct reduction are fed into a reducing plasma, for high energy and H2 efficiency at fast kinetics and high metallization.

Research Focus

Project ROC explores the physical and chemical foundations of these processes, down to atomistic scales, with a blend of instrumented laboratory furnaces, characterization, simulation, and machine learning. Specific topics include:

• Elementary nucleation, transport, and transformation mechanisms
• Mixed scrap and ore charging
• Influence of contaminants from feedstock
• Plasma parameters
• C-free electrodes
• Slag metallurgy
• The role of nanostructure

Conclusion

Drastic reduction of CO2 is the biggest challenge of our time, and project ROC explores how steelmaking can contribute to it by cutting its emissions by 80% and more.