Using Bionic Surfaces at a Blast Furnace

In blast furnaces, hot air at temperatures of around 1200 °C is blown into the reaction chamber for iron reduction and the smelting process. For this purpose, special water-cooled nozzles made of copper, called tuyeres, are used. These can be damaged or destroyed by glowing hot droplets of iron. Then energy- and cost-intensive repairs are necessary. Researchers have succeeded in designing the surface of these tuyeres so that liquid iron simply drips off. This new effect can be compared to the lotus effect on leaves. The most common reason for blast furnace downtime is burnt-through tuyeres. These are usually damaged when the surface of the tuyeres come into contact with molten pig iron flowing down. To minimize such damage, the researchers studied how they could develop a protective mechanism for the tuyeres that functions like the lotus effect. An ambitious goal as here it isn’t a matter of water droplets but keeping molten pig iron away from the copper surface. While the melting point of copper is 1084 °C, the surface of the tuyeres (cooled in an elaborate process) are exposed to 2300 °C in the blast furnace. With the structuring of the surface, the researchers wanted the copper tuyeres to be able to withstand the extreme temperatures prevailing in the blast furnace for a longer time. When molten metal at temperatures of 1500–1800 °C does not have long, intensive contact with the tuyeres, but simply drips off, the heat flow in the tuyeres is reduced substantially, and accordingly the danger of the tuyeres getting damaged or burning through is also mitigated. The longer service lifetime of the blast furnace tuyeres effects a reduction in unproductive energy input, CO2 emissions and operating costs.

The project funded by Germany’s Federal Ministry for Economic Affairs and Energy (BMWi) and entitled “Increasing Energy Efficiency in Blast Furnace Operation by Increasing Plant Availability with Novel Long-Life Tuyeres” will be concluded in the course of this year with field trials. A patent has already been applied for to protect the bionic surface structuring developed by the interdisciplinary group of researchers including the botanist Prof. Christoph Neinhuis and the physicist Dr Wilfried Konrad from the Biology Faculty at Dresden University of Technology and Dr Jörg Adam from VDEh Betriebsforschungsinstitut (BFI – Operational Research Institute of the German Steel Institute) together with Siegfried Konietzko from the tuyeres manufacturer Lebronze Alloys – Hundt & Weber.

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