Abatement of Chromium Emissions from Steelmaking Slags - Cr Stabilization by Phase Separation
2013 (English)Doctoral thesis, comprehensive summary (Other academic)
Chromium is an important alloying element in stainless steel but also environmentally harmful element. A number of mineralogical phases present in the slag matrix can contain chromium and lead to chromium leaching. Chromium in slag if not stabilized, could oxidize to the cancerogenic hexavalent state, and leach out if exposed to acidic and oxygen rich environment. Other environmental concerns are slag dusting and chromium escape to the atmosphere. Despite the fact that there is a certain risk of Cr-emission from slags at operating conditions, still very little is known regarding the emission of the oxides of chromium during the slag tapping. Spinel phase is known to be important for controlling the leaching properties of chromium from the slag. The objective of the present study was to get an understanding of the phase relationships and chromium partition in the chromium-containing industrial slags and synthetic slags with a view to control the chromium stabilization in spinel phase. The impact of slag basicity, heat treatment, oxygen partial pressure and Al2O3 addition, on the phase relationships and chromium partition has been determined. The experimental results were compared with the phase equilibrium calculations. It was found that the oxygen partial pressure in the gas phase had a strong impact on chromium partition. The experimental results show that the impact of the slag basicity on chromium partition at lower oxygen partial pressures was negligible in contrast to that in air. The amount of spinel phase was found to increase with increased Al2O3 content. Slow cooling of slag and soaking at low oxygen partial pressure would improve the spinel phase precipitation. This treatment will also lead to less Cr dissolved in the unstable matrix phases. Chromium oxide was found to be emitted when chromium containing slags were exposed to oxidizing atmosphere. The results indicate that chromium oxide evaporation increases with increase in temperature and oxygen partial pressure, but decreases with slag basicity and sample thickness.
Place, publisher, year, edition, pages
Stockholm: KTH Royal Institute of Technology, 2013. , xi, 53 p.
spinel; slag basicity; oxygen partial pressure; chromium oxide vaporization
шпинель; шлак; парциальное давление кислорода, испарение оксидa хрома
spinell, slaggbasicitet, syrepartialtryck, förångning av kromoxid
Metallurgy and Metallic Materials
IdentifiersURN: urn:nbn:se:kth:diva-133480ISBN: 978-91-7501-666-5OAI: oai:DiVA.org:kth-133480DiVA: diva2:661947
2013-12-06, B3, Brinellvägen 23, KTH, Stockholm, 10:00 (English)
Brabie, Voicu, Professor
Teng, Lidong, DocentSeetharaman, Seshadri, Professor
FunderMistra - The Swedish Foundation for Strategic Environmental ResearchKnut and Alice Wallenberg Foundation
QC 201311142013-11-142013-11-052013-11-14Bibliographically approved
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