Even before the cement and chemical industries, steel production accounts for the lion's share of industry-related global CO2 emissions. However, if researchers at the Karlsruhe Institute of Technology (KIT) have their way, this will soon change. Together with its industrial partner SMS group, KIT wants to drive forward a new process that can save several hundred million tons of CO2 per year in global steel production. This process is based on the modernization of existing blast furnace technology with moderate investments and has already been successfully demonstrated in a pilot plant, as the researchers recently reported in the journal Energy Advances.

Intermediate steps also lead further

The steel industry is responsible for around eight percent of total global CO2 emissions. "This has to change - and quickly," says Professor Olaf Deutschmann from the Institute of Technical Chemistry and Polymer Chemistry (ITCP) at KIT. In the long term, there is a climate-neutral perspective thanks to new hydrogen technologies, but it will be several years before sufficient green hydrogen is available worldwide and newly built plants are put into operation: "We don't have time for this in the climate crisis, we have to take countermeasures now." A significant savings effect could also be achieved in conventional plants in the short term with a new process that a research group under his leadership has demonstrated together with the industrial partner SMS group with Paul Wurth Entwicklungen and the startup omegadot from KIT. "The potential is enormous. We expect that retrofitting existing blast furnaces could save around two to four percent of global direct CO2 emissions at moderate investment costs," says Deutschmann.

New process reduces emissions and saves energy

The new process starts with the raw material iron, which steelworks usually extract directly from mining ores, where it is present in oxidized form. Reduction, i.e. the removal of oxygen, is usually carried out using coke in the blast furnace. This not only supplies the necessary energy for the melt as fuel, but also serves as a reducing agent for the chemical reaction. "Coke is extracted from fossil coal in an energy-intensive process specifically for this purpose," says Philipp Blanck from ITCP, who worked closely with SMS group on the pilot plant integrated into the steelworks. "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."

Significant amounts of coke can be saved

To retrofit an existing plant, existing hot blast furnaces, 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 into 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 the iron oxide. "Significant amounts of coke can be saved per tonne of steel produced, which in turn reduces specific CO2 emissions by up to twelve percent," says Blanck.

Successful demonstration with industrial partners

The process was demonstrated and validated at Aktien-Gesellschaft der Dillinger Hüttenwerke in Saarland. The transfer was also made possible by the collaboration with omegadot software & consulting GmbH, a spin-off from the KIT. The start-up, which specializes in industrial software, has developed software that enables precise simulation and visualization of the process and significantly supports the scale-up to an industrial plant.

An important first step that must be followed by others

The pilot plant is operated in Dillingen by SMS group together with its partners Dillinger and Saarstahl, who want to produce steel with lower CO2 emissions. Gilles Kass from SMS group's research department is keen to emphasize that the new process used here only marks the beginning of a comprehensive rethink in the steel industry: "The integration of the new process into the plant will only be the first step in the transformation of the steel industry."

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