LiDONIT 51 A mineral substance with potential In the tilting process from the converters, the slag is separated from the crude steel. Blown-in oxygen swirls quartz sand together with the slag into a valuable raw material. LiDonit cools down for one week in the bed before being stored in its processed form as a finished product.
52 LiDONIT the earth slowly and over years and millenniums took its (presently cooled) shape. Yet the converter not only produces the valuable crude steel mass, but also the slag, which is all too often referred to a waste product. “When the container is emptied, the crude steel is separated from the slag,” explains Joost. In the tilting process, the converter tilts to the left and then to the right, and 27 tons of the reddish-yellow, simmering slag are poured into the waiting hoppit – which slowly rolls away moments later, to the only plant in the world where the Linz-Donawitz slag is stabilized. WHY LIDONIT IS A VALUABLE MINERAL SUBSTANCE Seeing the later, final form of LiDonit is amazing – a granulated material that, in expert speak, is “cracked down” to different granulations in large breakers like those used in quarries. Which still does not tell us where the synthetic mineral substance will eventually be used: as a core component of an asphalt cover on roads. “The stabilized slags display a very high level of volume stability and equally strong firmness,” says DSU’s Joost. “In the sense of sustainable usage, LiDonit is an ideal material that should be just as interesting for road builders as for environmental politicians” concerned about conserving resources, he adds. For not only the steel, but also the slag as such is a product with value creation potential – what more can you expect of a basic material these days? Especially when communities do not want “slag heaps” scarring the countryside? Two <strong>ThyssenKrupp</strong> divisions cooperate on this process. Carl- Heinz-Schütz, the director for the metallurgy and heavy plate business A slag with a strong grip in the crude steel division and the holder of a doctorate in engineering, makes no secret of his satisfaction that this use for slag has been found. Schütz, who is in his late fifties, conveys the sort of laid-back attitude that one would associate with the rhythmically regulated processes in the steel works. As always, calmness exudes strength – which, however, is no argument against speed. Schütz reports that the steel experts welcomed the idea at the end of the 1990s to produce fine chippings “by using a lance injector to blow in oxygen and, without a mechanical stirrer, swirl the quartz sand to stabilize the slag.” The silicon dilutes the slag, because, as Schütz explains, “The lower the ratio of calcium to silicon oxide, the more fluid the slag. By mixing in quartz sand, free chalk particles are bound in the calciumsilicate.” It is a process that cannot be observed without special protection. The lance injector creates such a gleaming white light that color filters on goggles are needed to protect the eyes from lasting damage. Nearly 15 minutes later, the LiDonit mass is ready. And then? According to Joost, the idea for this mineral substance came from an attempt to find a sensible use for chalk-rich slags that otherwise cannot be used in road construction. “In this way we increasingly return mineral substances to the natural cycle. Slags with a high share of free chalk particles, which normally cannot be used because of their volume instability, are becoming really interesting for road builders.” Steel works No. II could produce 200,000 tons of LiDonit through the stabilization process, and according to Joost the demand is increasing. At present, 120,000 tons of blistering hot, stabilized LD slag leaves the works every year to be left to change from a liquid state into a solid state just a few hundreds meters away. Beds have been created for this purpose – not the sort of beds we think of in association with TK <strong>Magazin</strong>e | 1 | 2004 |
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