RWTH: Hydrogen as a fuel in the steel industry: RWTH involved in FlexHeat2Anneal joint project

How can hydrogen as a fuel reduce CO2 emissions in the steel industry? As part of the “FlexHeat2Anneal” joint project, the Institute for Industrial Furnace Construction and Heat Engineering at RWTH Aachen University, headed by Professor Herbert Pfeifer, is researching the sub-project “Investigation and optimization of the radiant tube system, operational measurements and life cycle assessments”. The Federal Ministry of Economics and Climate Protection is funding work with around 380,000 euros until March 2025.


The aim of the research project is the flexible use of hydrogen as a fuel in annealing lines and hot-dip coating systems for steel strip in order to reduce CO2 emissions there. For this purpose, the use of hydrogen in existing radiant tube systems is being investigated in the laboratory and at the same time the development and demonstration of innovative, fuel-flexible and energy-efficient so-called FLOX radiant tube systems with the lowest NOx emissions is being sought. The use of hydrogen in natural gas should be possible in the range from 0 to 100 percent by volume without the need for manual adjustments to the entire system. The aim is to achieve high process stability, energy efficiency and the lowest NOx emissions at the same time, despite the flexible and temporally fluctuating use of both fuels during combustion in the radiant heating tube.

thyssenkrupp Steel Europe AG and thyssenkrupp Rasselstein GmbH alone operate 14 of the 20 hot-dip coating plants and continuous annealing lines in Germany. The annual production capacity of these plants in Germany is around eight million tons of steel. So far, hydrogen as a fuel has not been tested at any of the plants. With a complete conversion of all plants to hydrogen, around 420,000 tons of CO2 could be saved throughout Germany every year. However, the desired combustion system should also be applicable even when the availability of green hydrogen is low. In the future, the aim is to work with green hydrogen, i.e. hydrogen produced with electricity from renewable energies, as a fuel.

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