Metallurgical and Materials Transactions B

, Volume 44, Issue 2, pp 244–251 | Cite as

Trace Elements in the Si Furnace-Part II: Analysis of Condensate in Carbothermal Reduction of Quartz

  • Elena Dal Martello
  • Gabriella Tranell
  • Oleg Ostrovski
  • Guangqing Zhang
  • Ola Raaness
  • Rune Berg Larsen
  • Kai Tang
  • Pramod Koshy


Silicon feedstock for production of solar-grade silicon should be as pure as possible to decrease the cost of manufacturing of solar cells. Impurities in quartz, carbonaceous materials, electrodes, and refractories are mostly present in the form of oxides. These oxides can be reduced to volatile gaseous compounds in presence of SiO(g) and CO(g) atmosphere and potentially leave the furnace or stay in the condensed reaction products, metal, and slag. This work investigates the conditions under which volatile impurities report to the gas phase in laboratory experiments with lumpy and pelletized mixtures of SiO2, SiC, and Si at 1923 K and 2123 K (1650 °C and 1850 °C), respectively, were carried out. The volatile compounds were generated by the reduction of quartz and collected in the form of condensate. The effects of the reaction temperature, quartz type, charge composition, pellets, and lumps on the composition of the condensate were studied. The trace elements in the charge input, reacting charge, and condensate were analyzed using inductively coupled plasma (ICP)-mass spectroscopy (MS) and X-ray diffraction (XRD). CO(g) and SiO(g), which are the major components in reduction reactions, formed four types of condensate: white, brown, green, and orange. The condensate constituents were amorphous SiO2, 3C:SiC, Si, and α-quartz. Each impurity present in the quartz charge entered the gas phase during quartz reduction and was detected in the condensate. Al and Fe show limited volatility. The volatility of Mn, P, and B depends on the charge mix: a higher PCO enhances the concentration of these elements in the gas phase. Fluid inclusions, common in hydrothermal quartz, enhance the distribution of the contaminants to the gas phase. Industrial campaigns on Si and Fe-Si production confirm the experimental results.


Volatility Fluid Inclusion Carbothermal Reduction Gaseous Compound Measured Volatility 
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.



The authors acknowledge John Sharp, Xing Xing, and Xiaohan Wan for their excellent technical help and productive discussions. This research work has been supported by ELKEM’s research fund.


  1. 1.
    E.H. Myrhaug: Non-Fossil Reduction Materials in the Silicon Process-Properties and Behaviour, NTNU, Trondheim, Norway, 2003.Google Scholar
  2. 2.
    M. Garcia and E.H. Myrhaug: Revisjon av Materialbalanse for Sporelementer i Si-ovn Basert på Målekampanje på Elkem Thamshavn April 2007, Elkem Silicon, Oslo, Norway, 2007.Google Scholar
  3. 3.
    H. Tveit and E. Myrhaug: Silicon for the Chemical Industry V. Tromsø, Norway, 2000, pp. 23–31.Google Scholar
  4. 4.
    E.H. Myrhaug and H. Tveit: Electric Furnace Conference Proceedings, American Institute of Mining and Metallurgical Engineers, New York, 2000, p. 58.Google Scholar
  5. 5.
    R.J. Ishak: Reaction Kinetics for Reduction of Manganese Ore with Carbon Monoxide in the Presence of Carbon, NTNU, Trondheim, Norway, 2002.Google Scholar
  6. 6.
    Y.E. Lee and D.S. Kozak: Electric Furnace Conference Proceedings, 1993, pp. 145–50.Google Scholar
  7. 7.
    J. Sterneland: Alkalis in the HCFeMn-Furnace, a Mass Balance of Potassium Oxide on the Furnace No 12 at Elkem Mangan a.s. PEA, Royal Institute of Technology, KTH, Stockholm, Sweden, 1993.Google Scholar
  8. 8.
    A. Schei, J.K. Tuset, and H. Tveit, eds.: Production of High Silicon Alloys, Tapir Forlag, Trondheim, Norway, 1998.Google Scholar
  9. 9.
    T. Førland and H. Flood, eds.: Selected Topics in High Temperature Chemistry. A Collection of Papers Dedicated to Professor Håkon Flood on His 60th Birthday, 25. Septemebr 1965, Universitetsforlaget, Oslo, Norway, 1966.Google Scholar
  10. 10.
    V. Andersen and M. Tangstad: Small Scale Laboratory Experiments Simulating an Industrial Silicon Furnace, in Infacon XII. Helsinki, Finland, 2010.Google Scholar
  11. 11.
    W. Poch and A. Dietzel: Ber. Dtsch. Keram. Ges., 1962, vol. 39, pp. 413–26.Google Scholar
  12. 12.
    A. Schei: Tidsskr. Kjemi Bergv, 1967, vol. 27, pp. 152–58.Google Scholar
  13. 13.
    J. Vangskåsen: Condensate Formation in the Silicon Process, NTNU, Department of Materials Science and Engineering, Internal Report, Trondheim, Norway, 2011.Google Scholar
  14. 14.
    E. Dal Martello, G. Tranell, O. Ostrovski, G. Zhang, O. Raaness, R.B. Larsen, K. Tang, and P. Koshy: Metall. Mater. Trans. B, 2012, in press.Google Scholar
  15. 15.
    A. Albinati and B.T.M. Willis: J. Appl. Cryst., 1982, vol. 15, pp. 361–74.CrossRefGoogle Scholar
  16. 16.
    E. Dal Martello, G. Tranell, S. Gaal, O. Raaness, K. Tang, and L. Arnberg: Metall. Mater. Trans. B, 2011, vol. 42, pp. 939–50.CrossRefGoogle Scholar
  17. 17.
    M. Gemeinert, M. Gaber, I. Hager, and M. Willfahrt: Neues Jahrbuch Miner. Abh., 1992, vol. 165, pp. 19–27.Google Scholar
  18. 18.
    R.B. Larsen, I. Henderson, and P.M. Ihlen: Contrib. Mineral. Petrol., 2004, vol. 147, pp. 615–28.CrossRefGoogle Scholar
  19. 19.
    J.B. Fein, J.J. Hemley, W.M. D’Angelo, A. Komninou, and D.A. Sverjensky: Geochim. Cosmochim. Acta, 1992, vol. 56, pp. 3179–90.CrossRefGoogle Scholar

Copyright information

© The Minerals, Metals & Materials Society and ASM International 2012

Authors and Affiliations

  • Elena Dal Martello
    • 1
  • Gabriella Tranell
    • 1
  • Oleg Ostrovski
    • 2
  • Guangqing Zhang
    • 3
  • Ola Raaness
    • 4
  • Rune Berg Larsen
    • 5
  • Kai Tang
    • 4
  • Pramod Koshy
    • 2
  1. 1.Department of Materials Science and EngineeringNTNUTrondheimNorway
  2. 2.UNSW Materials Science and EngineeringSydneyAustralia
  3. 3.UOWWollongongAustralia
  4. 4.SINTEF Materials and ChemistryTrondheimNorway
  5. 5.Department of Geology and Mineral Resources EngineeringNTNUTrondheimNorway

Personalised recommendations