Preventing the emission of several hundred million tonnes of CO₂ in global steel production every year – this is the goal which researchers at the Karlsruhe Institute of Technology (KIT) and their industrial partner SMS group want to accelerate by means of a new process. This process is based on modernising existing blast furnace technology with moderate investments and has already been successfully demonstrated in a pilot plant. The researchers have issued a report in the journal Energy Advances.
The process was demonstrated and validated at the smelting works of Aktien-Gesellschaft der Dillinger Hüttenwerke (Dillinger) in the German state of Saarland. The transfer was also made possible through cooperation with omegadot software & consulting GmbH, a spin-off of KIT. The start-up, which specialises in software for industrial purposes, is developing software which allows for the precise simulation and visualisation of the process and provides significant support for a scale-up to the size of an industrial plant. The pilot plant is operated in Dillingen by the SMS group together with its partners Dillinger and Saarstahl, who want to produce steel with fewer carbon emissions.
Steel industry causes eight percent of global carbon emissions
“It is important to emphasise that integrating the new process into the works is only the first step on the way to transforming the steel industry”, says Gilles Kass from the research department at SMS group, who also contributed to the report. Around eight percent of global carbon emissions are caused by the steel industry.
“This has to change – and fast”, says Professor Olaf Deutschmann from the Institute for Chemical Technology and Polymer Chemistry (ITCP) at KIT. While the new hydrogen technologies offer a climate-neutral option in the long term, it will be several years until there is enough green hydrogen available worldwide and newly constructed plants can be commissioned: “In a climate crisis, there is no time for that. We have to act now.”
The novel process offers a quick method to achieve a significant effect even in conventional plants, as his research team has demonstrated together with industrial partner SMS group as well as Paul Wurth Entwicklungen and the start-up omegadot from KIT.
“The potential is enormous. We expect that, by retrofitting existing blast furnaces at moderate investment costs, we could prevent approximately two to four percent of global direct carbon emissions”, says Deutschmann.
Novel process reduces emissions and saves energy
The novel process targets the raw material iron, which steelworks usually obtain directly from mined ore that contains oxidised iron. Usually, the reduction, i.e. the removal of oxygen, is carried out in a blast furnace utilising coke. Coke not only works as a fuel to supply the necessary energy for smelting, it also serves as a reduction agent for the chemical reaction.
“Coke is obtained from fossil coal specifically for this purpose using an energy-intensive process”, says Philipp Blanck from ITCP, who has cooperated closely with SMS group on the integrated pilot plant in the steelworks. “Our process recycles CO₂ from the blast furnace gas using coke oven gas, which produces a synthesised gas containing a high amount of hydrogen, which can then be used inside the blast furnace as a substitute for coke.”
In order to retrofit an existing plant, any existing hot air generators, called cowpers, need to be adapted. Inside these cowpers, methane and CO₂ from the coke oven gas are added to the CO₂ from the blast furnace gas and become synthesised gas, a mix of hydrogen and carbon monoxide.
This process, called dry reforming, necessitates a high temperature, which is achieved mainly by using the process heat of the blast furnace. The synthesised gas is then injected into the blast furnace, where it facilitates the reduction of the iron oxide. “This means saving a significant amount of coke for each tonne of steel that is produced, which in turn lowers specific carbon emissions by up to twelve percent”, says Blanck.
“It is important to emphasise that integrating the new process into the works is only the first step on the way to transforming the steel industry”, says Gilles Kass from the research department at SMS group, who also contributed to the report.
