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Metallurgical Transactions B

, Volume 24, Issue 6, pp 987–995 | Cite as

The reduction mechanism of chromite in the presence of a silica flux

  • P. Weber
  • R. H. Eric
Pyrometallurgy

Abstract

The reduction behavior of a natural chromite from the Bushveld Complex of South Africa was studied at 1300 °C to 1500 °C. Reduction was by graphite in the presence of silica. Thermo-gravimetric analysis, X-ray diffraction (XRD) analysis, energy-dispersive X-ray analysis (EDAX), and metallographic analysis were the experimental techniques used. Silica affected the reduction at and above 1400 °C. A two-stage reduction mechanism was established. The first stage, up to a reduction level of about 40 pct, is primarily confined to iron metallization, and zoning is observed in partially reduced chromites. In this stage, silica does not interfere with the reduction, which proceeds by an outward diffusion of Fe2+ ions and an inward diffusion of Mg2+ and Cr2+ ions. The second stage is primarily confined to chromium metallization, and formation of a silicate slag alters the reduction mechanism. The slag phase agglomerates and even embeds partially reduced chromite particles. An ion-exchange reaction between the re-ducible cations (Cr3+ and Fe2+) in the spinel and the dissolved cations (Al3+ and Mg2+) in the slag allows further reduction. Once the reducible cations are dissolved in the slag phase, they are reduced to the metallic state at sites where there is contact with the reductant.

Keywords

Metallurgical Transaction Chromite Metallic State Slag Phase Outward Diffusion 
These keywords were added by machine and not by the authors. This process is experimental and the keywords may be updated as the learning algorithm improves.

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References

  1. 1.
    Krupp Patent: Process for the Production of Ferrochromium, Application for S.A. Patent 8, 410, 101, Tried Krupp GmbH, 1984.Google Scholar
  2. 2.
    O. Soykan. R.H. Eric, and R.P. King:Metall. Trans. B, 1991, vol. 22B, pp. 53–63.Google Scholar
  3. 3.
    O. Soykan, R.H. Eric, and R.P. King:Metall. Trans. B, 1991, vol. 22B, pp. 801–10.CrossRefGoogle Scholar
  4. 4.
    H.G. Katayama, M. Tokuda, and M. Ohtani:Trans. Iron Steel lnst. Jpn., 1982, vol, 22 (3), p. B77.Google Scholar
  5. 5.
    N.F. Dawson: Ph.D. Thesis, University of Natal, Durban, Republic of South Africa, 1989.Google Scholar
  6. 6.
    N.L. Woollacott: Report No. 1950, National Institute for Metallurgy. Randburg, Republic of South Africa, 1978.Google Scholar
  7. 7.
    H.T.T. Tsai: Ph.D. Thesis, The Pennsylvania State University, State College, PA. 1981.Google Scholar
  8. 8.
    M. Akyuzlu and R.H. Eric:J. S. Afr. Inst. Min. Metall., 1992, vol. 92 (4). pp. 101–10.Google Scholar
  9. 9.
    A. Novakova. C. Kleir, and J.S. Jim: inReactivity of Solids, G.M. Schwab, ed., Elsevier, New York, NY, 1965, pp. 269–76.Google Scholar
  10. 10.
    O. Katsutoshi and S. Awazu:J. Phys. Chem. Solids, 1968, vol. 29, pp. 1269–73.CrossRefGoogle Scholar
  11. 11.
    A. Muan: inMintek 50, Proc. Int. Conf. Minerals Science and Technology, vol. 2, L.F. Haughton, ed., Council for Mineral Technology, Randburg, Republic of South Africa, 1985, pp. 897–904.Google Scholar
  12. 12.
    K. Morita and A. Inoue:Tetsu-to-Hagané, 1988, vol. 74, pp. 999–1005.Google Scholar
  13. 13.
    K. Morita and N. Sano:Tetsu-to-Hagané, 1988, vol. 74, pp. 133–35.Google Scholar
  14. 14.
    I. Barin. O. Knacke, and O. Kubaschewski:Thermochemical Properties of Inorganic Substances, Springer-Verlag, Berlin, 1977.Google Scholar
  15. 15.
    J.D. Tretjakow and H. Schmalzried:Ber. Bunsen-Ges. Phys. Chem., 1966, vol. 69 (5), pp. 396–402.Google Scholar
  16. 16.
    N. Toker and L.S. Darken:Geochim. Cosmochim. Acta, 1975, vol. 39. pp. 847–52.CrossRefGoogle Scholar
  17. 17.
    H. Schmalzried:Solid State Reaction, Academic Press, New York, NY, 1974.Google Scholar

Copyright information

© The Minerals, Metals & Material Society 1993

Authors and Affiliations

  • P. Weber
    • 1
  • R. H. Eric
    • 1
  1. 1.Department of Metallurgy and Materials EngineeringUniversity of the WitwatersrandJohannesburgSouth Africa

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