ThyssenKrupp Magazin

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 ThyssenKrupp 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 Magazine | 1 | 2004 |