In order to save several hundred million tons of CO2 per year in global steel production, researchers from the Karlsruhe Institute of Technology (KIT) and the industrial partner SMS group want to advance a new process. This is based on the modernization of existing blast furnace technology with moderate investments and has already been successfully demonstrated in a pilot plant. The researchers report in the journal Energy Advances.
The steel industry is responsible for around eight percent of global CO2 emissions. Professor Olaf Deutschmann from the Institute for Technical Chemistry and Polymer Chemistry (ITCP) at KIT is of the opinion that this must change quickly. In the long term, there is a climate-neutral perspective thanks to new hydrogen technologies, but it will still be a few years before sufficient green hydrogen is available worldwide and newly built plants go into operation.
“We don’t have time for this in the climate crisis, we have to take countermeasures now. The potential is enormous. We expect that by retrofitting existing blast furnaces, around two to four percent of global direct CO2 emissions can be saved with moderate investment costs,” says Deutschmann.
Reduced emissions
The new process starts with the raw material iron, which the steelworks usually obtain directly from mining ores in which it is present in oxidized form. The reduction, i.e. the removal of oxygen, usually takes place using coke in a blast furnace. This not only provides the necessary energy for the melt as a fuel, but also serves as a reducing agent for the chemical reaction.
“Coke is produced specifically for this purpose from fossil coal in an energy-intensive process. In our process, we recycle CO2 from the blast furnace gas with coke oven gas to produce a synthesis gas with a high hydrogen content that can be used as a coke substitute in the blast furnace,” explains Philipp Blanck from ITCP.
In order to retrofit an existing system, existing hot blast generators, also known as cowpers, must be modified. In these cowpers, methane and CO2 from the coke oven gas are then converted together with CO2 from the blast furnace gas to produce synthesis gas, a mixture of hydrogen and carbon monoxide. This process, known as dry reforming, requires a high temperature, which is largely obtained from the process heat of the blast furnace. The synthesis gas is then blown into the blast furnace where it supports the reduction of iron oxide.
“Significant amounts of coke can be saved per ton of steel produced, which in turn reduces specific CO2 emissions by up to twelve percent,” says Blanck.
Successfully carried out demonstration
The process was demonstrated and validated at the Aktien-Gesellschaft der Dillinger Hüttenwerke (Dillinger) in Saarland. The transfer was also made possible through collaboration with omegadot software & consulting GmbH, a spin-off from KIT. The start-up, which specializes in industrial software, develops software that enables precise simulation and visualization of the process and significantly supports the scale-up to an industrial plant. The pilot plant is operated in Dillingen by SMS group together with its partners Dillinger and Saarstahl, who want to produce steel with fewer CO2 emissions.
“It is important to emphasize that the integration of the new process into the plant will only be a first step in the transformation of the steel industry,” says Gilles Kass from the research department at SMS group.
