De-phosphorization in the DRI-EAF steelmaking and the effect of alumina

Mohammed A. Tayeb, Richard Fruehan, Seetharaman Sridhar

Research output: Chapter in Book/Report/Conference proceedingConference contribution

3 Scopus citations

Abstract

Flexibility in raw material, opportunity for the reduction in natural gas prices due to progress in shale gas extraction, and increased use of non-conventional electric arc furnace (EAF) steelmaking using up to 100% direct reduced iron (DRI) has prompted a renewed interest in better control of phosphorus (P). Iron ore, and consequently DRI, has higher phosphorus (up to 0.15wt.%[1]), and more silica, as compared to scrap. Significant work has been done on understanding the partitioning of phosphorus between slag and metal for slags with chemistries relevant to those used in Basic Oxygen Furnace (BOF). However, there is little reported work on slag chemistries corresponding to that in the EAF when DRI is used. In the current work, phosphorus equilibrium between molten Fe-P alloys and slags relevant to the EAF-DRI process was investigated. It is found that the existing correlations cannot be extended to EAF-DRI conditions. The existing correlations do not contain Al 2O3, which will be present for the DRI-EAF process. A new version of the equilibrium phosphorus-partitioning equation which includes alumina is presented. The phosphorus partitioning has been shown to decrease in magnitude due to the effect of alumina. Adding as low as 2.5 wt.% alumina decreases the phosphorus partition by more than a factor of two. Having a slag with higher than 13 wt.% alumina remarkably lowers the phosphorus partition by over an order of magnitude. The observed effect of alumina is attributed to its high acidity which contributes to the reduction of the phosphorus capacity of the slag by lowering the activities of iron oxide and calcium oxide. This in turn lowers the dissolved and free oxygen which is needed for phosphorus to oxidize in order to partition to the slag phase. These results are applied to EAF plant data from international steelmakers, which indicates equilibrium is not achieved in the process, and is expected from the kinetic conditions in the furnace.

Original languageEnglish (US)
Title of host publicationAISTech 2014 - Proceedings of the Iron and Steel Technology Conference
PublisherAssociation for Iron and Steel Technology, AISTECH
Pages1073-1086
Number of pages14
ISBN (Print)9781935117421
StatePublished - 2014
Externally publishedYes
EventAISTech 2014 Iron and Steel Technology Conference - Indianapolis, IN, United States
Duration: May 5 2014May 8 2014

Publication series

NameAISTech - Iron and Steel Technology Conference Proceedings
Volume1
ISSN (Print)1551-6997

Conference

ConferenceAISTech 2014 Iron and Steel Technology Conference
Country/TerritoryUnited States
CityIndianapolis, IN
Period5/5/145/8/14

Keywords

  • Alumina
  • Dephosphorization
  • DRI
  • EAF
  • Equilibrium
  • Phosphorus partition

ASJC Scopus subject areas

  • Industrial and Manufacturing Engineering

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