Using Hydrogen as a Fuel in the Steel Industry: RWTH Involved in a Joint Project – FlexHeat2Anneal


How can using hydrogen as a fuel reduce CO2 emissions in the steel industry? In the joint project FlexHeat2Anneal, the Department for Industrial Furnaces and Heat Engineering at RWTH is conducting research headed by Professor Herbert Pfeifer on the sub-project: Investigation and Optimization of the Radiant Tube System, Operational Measurements, and Life Cycle Assessments. Thyssenkrupp Rasselstein GmbH and WS Wärmeprozesstechnik GmbH are the project partners. The German Federal Ministry of Economic Affairs and Climate Action is funding this research work with around 380,000 euros until March 2025.


The aim of the research project is the flexible use of hydrogen as a fuel on annealing lines and hot-dip coating lines for steel strip in order to reduce CO2 emissions there. For this purpose, the use of hydrogen in existing radiant tube systems is being researched in the laboratory. At the same time, the objective is to develop and demonstrate innovative, fuel-flexible, and energy-efficient so-called FLOX radiant tube systems with very low NOx emissions. The use of hydrogen in natural gas should be possible in the range of 0 to 100 percent by volume without the need for manual adjustments to the overall plant. The aim is to simultaneously achieve high process stability, energy efficiency, and very low NOx emissions despite the flexible and time-varying use of both fuels during combustion in the radiant tube heater. Thus, on the one hand, this project contributes to decarbonization efforts in the steel processing sector, and on the other hand, the acceptance of hydrogen as a fuel in industry.

Thyssenkrupp Steel Europe AG and thyssenkrupp Rasselstein GmbH alone operate 14 of the 20 hot-dip coating lines and continuous annealing lines in Germany. The annual production capacity of these German plants is around eight million tons of steel. To date, hydrogen fuel has not been tested at any of the plants. A complete conversion of all plants to hydrogen could see Germany save around 420,000 tons of CO2 annually. The envisioned combustion system should, however, be applicable even with low availability of green hydrogen. The aim is to use green hydrogen, i.e. hydrogen produced using electricity from renewable sources, as a fuel in the future.