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A model for activity coefficient of P2O5 in BOF slag and phosphorus distribution between liquid steel and slag
KTH, School of Industrial Engineering and Management (ITM), Materials Science and Engineering.
KTH, School of Industrial Engineering and Management (ITM), Materials Science and Engineering, Materials Process Science.
2007 (English)In: ISIJ International, ISSN 0915-1559, E-ISSN 1347-5460, Vol. 47, no 8, p. 1236-1238Article in journal (Refereed) Published
Place, publisher, year, edition, pages
2007. Vol. 47, no 8, p. 1236-1238
Keywords [en]
IRON
National Category
Metallurgy and Metallic Materials
Identifiers
URN: urn:nbn:se:kth:diva-7303DOI: 10.2355/isijinternational.47.1236ISI: 000248992600022Scopus ID: 2-s2.0-35348856814OAI: oai:DiVA.org:kth-7303DiVA, id: diva2:12271
Note
QC 20100623Available from: 2007-06-07 Created: 2007-06-07 Last updated: 2017-12-14Bibliographically approved
In thesis
1. Studies on dephosphorisation during steelmaking
Open this publication in new window or tab >>Studies on dephosphorisation during steelmaking
2007 (English)Doctoral thesis, comprehensive summary (Other scientific)
Abstract [en]

This work is aimed at understanding the thermodynamic principles influencing the phosphorus partition between slag and steel during steelmaking, particularly during refining of high-phosphorus hot metal using the basic oxygen steelmaking (BOS) process. Mapping of the slag path has been carried out using a mass balance model based on input conditions and off-gas analysis, which has been validated by intermediate measurements of slag and metal composition in an industrial basic oxygen furnace (BOF). The slag composition is found to vary over a wide range of basicity (%CaO/%SiO2) and iron oxide content. The partition of phosphorus increases with progress of refining but reduces during the intermediate period, corresponding to a decrease in iron oxide concentration and formation of “dry slag”. The phosphorus partition ratio increases again towards the end of the process. The equilibrium partition ratios for such conditions have been theoretically estimated using slag “model(s)”, based on the estimated slag compositions. It is seen that the partition ratio of phosphorus remains within 45% – 60% of the equilibrium value, showing a gradual decrease with progress of the refining process.

Equilibrium phosphorus partition ratios for slags containing low concentrations of MnO and Al2O3 have been experimentally determined, over the ranges of basicity and iron oxide concentration approximately corresponding to that observed in the typical BOS process. It is seen that the equilibrium phosphorus partition ratio is practically independent of basicity greater than 2.5 – 2.6, over the entire range of temperature and FeOx concentration studied. Variation of the activity of P2O5 with basicity and FeOx concentration has been investigated to explain the trends observed in the variation of phosphorus partition ratio. It is seen that the activity coefficient of P2O5 is lowest, and hence most conducive for removal of phosphorus from steel, over certain finite ranges of basicity and iron oxide concentration. It follows that the efficiency of dephosphorisation is likely to be maximum if the basic oxygen steelmaking process is operated within these ranges. Simultaneous with this work, mathematical correlations have been developed for estimation of P2O5 activity coefficient and phosphorus partition ratio as functions of slag composition. The correlations are compared with those proposed by earlier workers and are found to result in better predictions over certain composition ranges.

Place, publisher, year, edition, pages
Stockholm: KTH, 2007
National Category
Metallurgy and Metallic Materials
Identifiers
urn:nbn:se:kth:diva-4427 (URN)978-91-7178-708-8 (ISBN)
Public defence
2007-06-15, Sal B1, KTH, Brinellvägen 23, Stockholm, 14:00
Opponent
Supervisors
Note
QC 20100623Available from: 2007-06-07 Created: 2007-06-07 Last updated: 2012-03-19Bibliographically approved

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