Nachbehandlung von Stahlwerksschlacken und deren Verwertung als Klinkermaterial
Post-treatment of steelmaking slags and their utilisation as cement clinker
- LD-Schlacken weisen eine große chemische Ähnlichkeit zu Protlandzementklinker auf. Sie enthalten jedoch noch bis zu 30% Eisen, das mineralisch in oxidischer Form gebunden vorliegt. Dadurch kann sich bei der Erstarrung die wichtigste Klinkerphase "Alit" nicht ausbilden. Durch eine reduzierende Schmelzbehandlung der Schlacke kann des mineralisch gebundene Eisen als Metall separiert werden. Dadurch wird auch die Mineralogie der Schlacke so verändert, dass auch sie nun praktisch einem Portlandzementklinker entspricht. Entsprechende Versuche wurden am kleintechnischen Lichtbogenofen der BAM durchgeführt. Es werden Ergebnisse vorgestellt und auf Grenzen und Möglichkeiten eines derartigen Prozesses im Hinblick auf eine industrielle Umsetzung eingegangen.
- Steelmaking slags produced using the Linz-Donawitz method (LD slags) are widely used as building and construction materials in road, earth and water works. Because the legal conditions become more and more re-strictive , this application is uncertain in the future.
LD slags contain high amounts of mineral bound iron (in form of Fe2O3), which must be considered as a waste of resources. Except for the Iron the chemical composition is quite similar to that of Portland cement clinker. However, due to the high content of Fe2O3 the mineralogical composition differs significantly, resulting in a low hydraulic reactivity. A post-treatment of the liquid LD slag in an electric arc furnace under reducing conditions enables the reduction of the iron compounds to metallic iron, which separates from the mineral phase due to its higher density. The remaining solidified mineral fraction mainly contains typical crystalline phases of cement clinker in similar ratios: Alite (Ca3SiO5; > 60%) as mainSteelmaking slags produced using the Linz-Donawitz method (LD slags) are widely used as building and construction materials in road, earth and water works. Because the legal conditions become more and more re-strictive , this application is uncertain in the future.
LD slags contain high amounts of mineral bound iron (in form of Fe2O3), which must be considered as a waste of resources. Except for the Iron the chemical composition is quite similar to that of Portland cement clinker. However, due to the high content of Fe2O3 the mineralogical composition differs significantly, resulting in a low hydraulic reactivity. A post-treatment of the liquid LD slag in an electric arc furnace under reducing conditions enables the reduction of the iron compounds to metallic iron, which separates from the mineral phase due to its higher density. The remaining solidified mineral fraction mainly contains typical crystalline phases of cement clinker in similar ratios: Alite (Ca3SiO5; > 60%) as main phase, Belite (Ca2SiO4, 10%), Tricalciumaluminate (Ca3Al2O6; 5%) and Brownmillerite (Ca2(Al,Fe)2O5, 1%) as secondary phases. Alite, which usually decomposes to Belite and free lime under slow cooling conditions, is stabilized in the Fe-reduced slag probably by integration of foreign ions into the lattice and is stable even if the slag is cooled down very slowly. Furthermore, the particularly large Alite crystals do not exhibit the typical decomposition edge of Belite and lime, found in Alite from ordinary ce-ment clinker. Technological tests for building materials show a high hydraulic reactivity and a compressive strength after 28 days comparable or even slightly higher to reference cement.
Nevertheless, because of the increasing viscosity with decreasing Fe2O3 content, the treatment requires a temperature higher than the slag decanted from the LD converter. Furthermore, during the reduction of the bound Iron huge amounts of carbon monoxide are released, resulting in foaming of the slag. Both aspects make it difficult to manage the process. In addition, for economic reasons the treatment has to be carried out immediately after casting the slag from the LD converter to avoid the solidification, which is a logistical challenge for most steel plants. Otherwise the separation of the mineral bound iron as metallic phase and the utilisation of the mineral fraction as cement clinker will both save resources and lower the global CO2-output. For these reasons further initiatives should be considered in the medium term.…
Autor*innen: | Burkart AdamczykORCiD, Katharina Schraut, Christian AdamORCiD |
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Persönliche Herausgeber*innen: | S. Thiel, E. Thomé-Kozmiensky, B. Friedrich, T. Pretz, P. Quicker, D. G. Senk, H. Wortruba |
Dokumenttyp: | Beitrag zu einem Tagungsband |
Veröffentlichungsform: | Verlagsliteratur |
Sprache: | Deutsch |
Titel des übergeordneten Werkes (Deutsch): | Mineralische Nebenprodukte und Abfälle 5 |
Jahr der Erstveröffentlichung: | 2018 |
Organisationseinheit der BAM: | 4 Material und Umwelt |
4 Material und Umwelt / 4.4 Thermochemische Reststoffbehandlung und Wertstoffrückgewinnung | |
Verlag: | Thomé-Kozmiensky Verlag GmbH |
Verlagsort: | Neuruppin |
Jahrgang/Band: | 5 |
Erste Seite: | 282 |
Letzte Seite: | 296 |
DDC-Klassifikation: | Technik, Medizin, angewandte Wissenschaften / Ingenieurwissenschaften / Sanitär- und Kommunaltechnik; Umwelttechnik |
Freie Schlagwörter: | Alit; LD-Schlacke; Lichtbogenofen; Stahlwerksschlacke; Zementklinker |
Themenfelder/Aktivitätsfelder der BAM: | Umwelt |
Umwelt / Circular Economy | |
Veranstaltung: | Berliner Konferenz Mineralische Nebenprodukte und Abfälle |
Veranstaltungsort: | Berlin, Germany |
Beginndatum der Veranstaltung: | 11.06.2018 |
Enddatum der Veranstaltung: | 12.06.2018 |
ISBN: | 978-3-944310-41-1 |
Verfügbarkeit des Dokuments: | Datei im Netzwerk der BAM verfügbar ("Closed Access") |
Datum der Freischaltung: | 20.06.2018 |
Referierte Publikation: | Nein |