Ammonia solves hydrogen steelmaking issues: German institute

Ammonia can be used to overcome the difficulties posed by storing and transporting hydrogen for use in green steelmaking, Germany’s non-profit Max Planck Institute says in a new report.

To ensure steelmaking is decarbonised, the energy and hydrogen used must be produced in sustainable ways. However, markets lack enough green hydrogen, while the current means of storing and transporting hydrogen demand high pressures and low temperatures, which are both costly.

By contrast, ammonia which can be formed with hydrogen, is already traded worldwide, with established logistics, and is known to be an excellent hydrogen carrier with low liquefaction costs.

“Our aim was to study whether ammonia can be directly used to reduce iron ores without cracking it into hydrogen and nitrogen,” Yan Ma, group leader at Max-Planck-Institut für Eisenforschung and primary author of the publication, says in a note seen by Kallanish. “Avoiding this cracking process can reduce the overall costs by 18%. Moreover, we analysed how ammonia as a reduction agent affects the properties of the reduced iron.”

“The ammonia-based direct reduction proceeds through an autocatalytic reaction. We compared its kinetics with the hydrogen-based direct reduction. Both have similar characteristics and yield the same metallisation degree. In contrast to hydrogen-based reduction, nitrides form during cooling in ammonia, which could protect the sponge iron from corrosion and make it easier to handle,” explains Ma.

The nitride phase can be completely dissolved and removed during the subsequent melting process, which is anyway requested for downstream processing. Moreover, the other product of ammonia decomposition, nitrogen, can act as a heat carrier in a shaft furnace to maintain the reaction temperature and enhance the efficiency for the reduction of iron ores. Already existing furnace technologies, such as shaft and electric arc furnaces, can be used with only slight modification, Max Planck concludes.

Adam Smith Poland