Climate-friendly Steel
Recycling CO2 in the Blast Furnace
© worldsteel/thyssenkrupp steel, Germany
Pictured: Coke oven in the integrated iron and steel mill of thyssenkrupp Steel Europe AG in Duisburg-Bruckhausen: Here volatile hydrocarbons are removed from the coal to recover carbon for use in the blast furnace.
Germany is the largest steel producer in the EU. Around a third of the carbon dioxide (CO2) emitted by all industry in Germany is produced in blast furnaces. But an alternative process route is in sight that produces almost no CO2. However, it will take many years before it is fully established. Under the coordination of the University of Duisburg-Essen (UDE), engineers are developing a concept for recycling the CO2 that is produced. The project is being funded by the German Federal Ministry of Education and Research.
In the coming decades, the large steel companies will switch to direct reduction plants, which will initially be operated with natural gas and later with hydrogen. In this process, iron ore is reduced to iron with the help of hydrogen. The subsequent melting process uses electricity generated from renewable sources. The resulting CO2 emissions are negligible at around 30 kg per ton of crude steel. But it will be decades before the corresponding infrastructure - from hydrogen production to predominantly CO2-free electricity generation - is fully in place.
In the transition phase, direct reduction produces high-purity CO2 as a byproduct that is to be reused in blast furnaces. In the next 20 to 30 years, the classic and new processes will coexist.
Engineers from the UDE are therefore working with thyssenkrupp Steel Europe AG and TU Clausthal to develop a concept for recycling CO2 directly in the process in the short term. The aim of the "NuCOWin" project is to answer the fundamental questions of process and plant technology for implementation on an industrial scale.
"The big challenge is to develop economical processes within the transformation in the steel industry, but also in other industrial sectors, that no longer release CO2 into the atmosphere," explains project leader Prof. Dr.-Ing. Rüdiger Deike from the UDE Institute for Technologies of Metals. "To do this, one should understand: Due to their high energy density, carbon compounds will continue to be indispensable, but the CO2 will remain in the cycle."
Within the funding program "KlimPro: Avoidance of climate-relevant process emissions in industry," the German Federal Ministry of Education and Research is funding the just-launched project for three years with a total of 1.2 million euros.