At ArcelorMittal's Hamburg steel mill, a granulate made from municipal waste is used instead of coal to produce crude steel from sponge iron and recycled scrap in an electric arc furnace. The crude steel, in turn, is the basis for the production of various steels ranging from reinforcing steel in the construction sector to wire for nails, screws, fences and springs to steel cables that give support to oil rigs, ski lifts and bridges. At ArcelorMittal Hamburg, two years of development were invested in the new process, and now around half of the coal previously used in the electric arc furnace is being replaced by a more resource-efficient alternative.
"We are saving 3,500 metric tons of direct CO2 emissions a year from now on with this project," says project manager Dr.-Ing. Michel Wurlitzer.
At the start of the project, engineers from ArcelorMittal worked with Stein Injection Technology GmbH from Gevelsberg in the Ruhr region, a technology supplier, to test various substitutes for their suitability.
"Among other things, we examined sewage sludge and paper fiber residues, processed orange peels and non-recyclable waste. Our colleagues at Stein Injection Technology assisted us with their injection technology to ensure the test materials were eligible," Wurlitzer says.
A residual granulate made from waste from private households and similar facilities provided the most convincing results. The CO2 reduction is made possible by the biogenic carbons it contains, which are present in paper or cotton fibers, for example, and by the hydrogen it contains. The high temperatures in the steel bath, which exceed 1600 degrees Celsius, are another advantage. These lead to complete decomposition of the granules.
"Our emissions tests show that the use of the substitute does not produce any measurable emissions," Wurlitzer said.
"The decarbonization of steel production is one of the most important cornerstones for achieving the climate targets in Europe," ArcelorMittal Hamburg Managing Director Dr. Uwe Braun is pleased to say.
