When it comes to sustainability and green steel, everybody talks about hydrogen. But current means of storing and transporting hydrogen request high pressures and low temperatures, which are both energetically and economically costly. Ammonia is known to be a good hydrogen carrier. Yan Ma and colleagues show that ammonia can not only be used to carry hydrogen but also for the direct redcution of iron which makes ammonia a vialbe cnadidate to overcome the shortcomings of hydrogen.
Steel production is currently the biggest single cause of global warming, responsible for ca. 7% of global CO2 emissions. To cut these emissions, scientists and industry are intensively investigating hydrogen-based ironmaking approaches as sustainable pathways to replace carbon reductants. While the hydrogen-based direct reduction of iron ore is promising, researchers are facing one major challenge: to make the whole steel making process climate friendly, the used energy and hydrogen themselves should be produced in sustainable ways. But markets are lacking enough green hydrogen and current means of storing and transporting hydrogen request high pressures and low temperatures, which are both energetically and economically costly. Researchers of the Max-Planck-Institut für Eisenforschung (MPIE) tackled this challenge by using ammonia as a hydrogen carrier and as a reductant for iron. They compared the iron and steel produced with ammonia-based direct reduction with hydrogen-based direct reduction, analysed the characteristics of the novel process and costs and published their results in the journal Advanced Science.
Ammonia as direct reductant brings several advantages
Future steel industry deploying intermittent renewable energy mediated by green ammonia.
© T. You, Max-Planck-Institut für Eisenforschung GmbH
Outlook: synthesizing green ammonia and tuning the iron reduction process
The ammonia-based direct reduction connects two of the most CO2 intensive industries, the steel and ammonia production, and paves the way to a sustainable transition together. Moreover, by using ammonia the logistic and energetic disadvantages of hydrogen are overcome and already existing furnace technologies, namely shaft and electric arc furnaces can be used with only slight modification. In the next step, the Max Planck team will test different process parameters like temperature or gas mixture to speed up the ammonia-based reduction process for a wide industrial application.
The research is supported by an Advanced Grant of the European Research Council for Prof. Dierk Raabe, director at MPIE, and by a grant for Yan Ma financed by the Walter Benjamin Programme.
Author: Yasmin Ahmed Salem
