A new process for production
of cement clinker from steelmaking slags
H. Wulfert, Loesche GmbH, Duesseldorf,
H. M. Ludwig, Bauhaus-Universität Weimar, Weimar, Germany,
G. Wimmer, Primetals Technologies, Linz, Austria
During typical LD (BOF) converter steel making about 120 kg of slag are produced per tonne of steel tapped. Conventional ways of utilization of these slags for the construction business or fertilizers are becoming less and less economically attractive due to stricter environmental regulations, decreasing market volume and decreasing prices. Furthermore, the typical way of processing the slag by simple pouring and cooling on the slag yard is for several steel plants no longer acceptable as it generates dust emissions, causes iron and energy losses and requires a lot of land. Hence, economically more attractive ways to market the slag, as well as closed processes for slag modification and handling that minimize dust emissions and footprint are required. A promising approach in this direction developed by Loesche, Primetals Technologies and partners is a modification of the LD slag in such a way that it can be used as a highly hydraulic active cement clinker substitute. This modification further allows recovery of almost the entire metallic content of the slag. A three-step process is used, in the first step the iron oxides in the slag are recovered in a reducing atmosphere and the clinker standard of the slag is adjusted. This is done by coal injection and electrical heating. In the second step the modified liquid slag is solidified in such a way that a considerable mass percentage of alite is formed. This alite leads to pronounced hydraulic properties of the slag, allowing the use of the modified slag as cement clinker substitute. In the last step the solid slag is ground and the remaining iron content is recovered. In this contribution a detailed description of the process itself including mass, energy and CO2 balances will be presented as well as results from testing and first layouts for a typical plant. Finally an economical evaluation of the entire process will be presented and discussed in detail.
Summary CEMENT INTERNATIONAL 01/2017 pp 46-51
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