Skip to main content
SpringerLink
Log in

Study on flow and mixing characteristics of molten steel in RH and RH-KTB refining processes

  • Materials Science And Engineering
  • Published:
Journal of Shanghai University (English Edition)

Abstract

The flow and mixing characteristics of molten steel during the vacuum circulation refining, including RH(Ruhrstahl-Heraeus) and RH-KTB(Ruhrstahl-Heraeus-Kawasaki top blowing) processes, were investigated on a 1/5 linear scale water model of a 90 t multifunction RH degasser. The circulation rate was directly and more accurately determined, using a new method by which the more reliable results can be obtained. The fluid flow pattern and flow field in the ladle were demonstrated, observed and analyzed. The mixing time of liquid in the ladle was measured using electrical conductivity method. The residence time distribution in the RH model was obtained by tracer response technique. The influence of the main technological and geometric factors, including the gas top blowing (KTB) operation, was examined. The results indicated that the circulation rate of molten steel in the RH degasser can be fairly precisely calculated by the formula: Q lp=0.0333Q 0.26g D 0.69u D 0.80d (t/min), where Q g - the lifting gas flow rate (NL/min); D u and D d - the inner diameters of the up and down-snorkels (cm), respectively. The maximum value of circulation rate of molten steel in the case of the 30 cm diameters either of the up-and down-snorkels for the RH degasser (the “saturated” rate) is approximately 31 t/min. The corresponding gas flow rate is 900 NL/min. Blowing gas into the vacuum chamber through the top lance like KTB operation does not markedly influence the circulatory flow and mixing characteristics of the RH process under the conditions of the present work. There exist a major loop and a large number of small vortices and eddies in the ladle during the RH refining process. A liquid-liquid two-phase flow is formed between the descending stream from the down-snorkel and the liquid around the stream. All of these flow situation and pattern will strongly influence and determine the mixing and mass transfer in the ladle during the refining. The correlation between the mixing time and the stirring energy density is τ m∞ε −0.50 for the RH degasser. The mixing time rapidly shortens with an increase in the lifting gas flowrate. At a same gas flow rate, the mixing times with the up-and down-snorkel diameters either of 6 and 7 cm are essentially same. The 30 cm diameters either of the up-and down-snorkels for the RH degasser would be reasonable. The concentration-time curve showed that three circulation cycles are at least needed for complete mixing of the liquid steel in the RH degasser.

This is a preview of subscription content, log in via an institution to check access.

Access this article

Log in via an institution

Price excludes VAT (USA)
Tax calculation will be finalised during checkout.

Instant access to the full article PDF.

Institutional subscriptions

Similar content being viewed by others

References

  1. Wtanabe H, Asano K and Saeki T. Some chemical engineering aspects of RH degassing process [J]. Tetsu-Hagané, 1968, 54(13): 1327–1342.

    Google Scholar 

  2. Fuji T and Mnchi I. Theoretical analysis on the degassing process in upper leg of RH degassing plant[J]. Tetsu-Hagané, 1970, 56(9): 1165–1171.

    Google Scholar 

  3. Tanaka B, Sakakibara M and Bayashi Z. Circulation rate characteristic of RH vacuum degassing process[J]. Iron Research, 1978,(293): 12427–12432.

  4. Katoh T and Okamoto T. Mixing of molten steel in ladle with RH reactor by the water model experiment [J]. Electric Furnace Steel, 1979, 50(2): 128–137.

    Google Scholar 

  5. Ono K, Yanagida M, Katoh T, et al. The circulation rate of RH-degassing process by water model experiment [J]. Electric Furnace Steel, 1981, 52(3): 149–157.

    Google Scholar 

  6. Seshadri V and De Souza Costa S L. Cold model studies of RH degassing process[J]. Transactions ISIJ, 1986, 26 (2): 133–138.

    Google Scholar 

  7. Kuwabara T, Umezawa K, Mori K, Watanabe H, et al. Investigation of decarburization behavior in RH-reactor and its operation improvement[J]. Transactions ISIJ, 1988, 28(4):305–314.

    Google Scholar 

  8. Hanna R K, Jones T, Blake R I and Millman M S. Water modelling to aid improvement of degasser performance for production of ultralow carbon interstitial free steels [J]. Ironmaking Steelmaking, 1994, 21(1):37–43.

    Google Scholar 

  9. Ahrenhold Frank, Pluschkell Wolfgang. Circulation rate of liquid steel in RH degassers [J]. Steel Research, 1998, 69(2):54–59.

    Google Scholar 

  10. Nakanishi K, Szekely J and Chang C W. Experimental and theoretical investigation of mixing phenomena in the RH-vacuum process [J]. Ironmaking Steelmaking, 1975, 2(5): 115–124.

    Google Scholar 

  11. Shirabe K and Szekely J. A mathematical model of fluid flow and inclusion process [J]. International ISIJ, 1983, 23(3): 465–474.

    Google Scholar 

  12. Tsujino R, Nakanishi J, Hirai M and Sawada I. Numerical analysis of molten steel flow in ladle of RH process [J]. ISIJ International, 1989, 29(7):589–595.

    Google Scholar 

  13. Szatkowaski M and Tsai M C. Turbulent flow and mixing phenomena in RH ladles: effect of the clogged down-leg snorkel[J]. Iron & Steelmaker, 1991, 18(4): 65–71.

    Google Scholar 

  14. Kato Y, Nakato H, Fujii T, et al. Fluid flow in ladle and its effect on decarburization rate in RH degasser [J]. ISIJ International, 1993, 33(10): 1088–1094.

    Google Scholar 

  15. Li B-K and He J-Ch. Numerical simulation on circulating flow and mixing of molten steel in RH degassing system employed a coupled domain-splitting and coordinate-interlocking technique [A]. 1994 (77th) Steelmaking Conference Proceedings[C]. Iron & Steel Society, USA, 723–727.

  16. Kamata C, Matsumura H, Miyasaka H, et al. Cold model experiments on the circulation flow in RH reactor using a laser doppler velocimeter[A]. 1998 (81 st) Steel-making Conference Proceedings [C]. Iron & Steel Society, USA, 609–616.

  17. Zhu M-Y, Jun Sh and Huang Z Z. Numerical simulation of molten steel flow in a RH degasser[J]. Acta Metallurgica Sinica, 2000, 36(11): 1175–1178.

    Google Scholar 

  18. Park Young-Geun, Doo Won-Chut, Yi Kyung-Woo and An Sang-Bok. Numerical calculation of circulation flow rate in the degassing Rheinstahl-Heraeus process [J]. ISIJ International, 2000, 40(8): 749–755.

    Google Scholar 

  19. Liu Zh-X, Chen Y-Sh, He Y-D, et al.. A mathematical model of molten steel circulation flow in RH vacuum re-fining[J]. J. Baotou University of Iron Steel Technology, 2001, 20(1): 23–26. (in Chinese)

    MATH  Google Scholar 

  20. Vargas G A, Silva C A Da and Tavares R P. Mathematical and physical modeling of CST S RH degasser ladle [A]. 2001 (84th) Steelmaking Conference Proceedings[C]. Iron & Steel Society, USA, 661–672.

  21. Xu Kuangdi, The circulation characteristic and stirring efficiency in RH-injection ladle [A]. Proceedings of 7th International Conference on Vacuum Metallurgy, Tokyo, Japan 1982: 1391–1403.

  22. WEI Ji-He, YU Neng-Wen. Mathematical modeling for RH refining process of molten steel[J]. Steel Research, 2002, 73(4):135–148.

    Google Scholar 

  23. Nakanishi K, Fujii T and Szekely J. Possible relationship between energy dissipation and agitation in steel processing operation[J]. Ironmaking Steelmaking, 1975, 2: 193–197.

    Google Scholar 

  24. Asai S, Okamato T, He J C and Muchi I. Mixing time of refining vessel stirred by gas injection [J]. Transactions ISIJ, 1983, 23(1): 43–50.

    Google Scholar 

  25. Zhang Jian. The Theory and Practice of Out-Furnace Refining[M]. Metallurgical Industry Press, Beijing, P. R. China, 1993: 547. (in Chinese)

    Google Scholar 

Download references

Author information

Authors and Affiliations

  1. College of Materials Science and Engineering, Shanghai University, 200072, Shanghai, China

    Wei Ji-He Ph. D. (Prof.), Yu Neng-Wen, Fan Yang-YI, Yang Sen-Long, Ma Jin-Chang & Zhu De-Ping

Authors
  1. Wei Ji-He Ph. D.
    View author publications

    You can also search for this author in PubMed Google Scholar

  2. Yu Neng-Wen
    View author publications

    You can also search for this author in PubMed Google Scholar

  3. Fan Yang-YI
    View author publications

    You can also search for this author in PubMed Google Scholar

  4. Yang Sen-Long
    View author publications

    You can also search for this author in PubMed Google Scholar

  5. Ma Jin-Chang
    View author publications

    You can also search for this author in PubMed Google Scholar

  6. Zhu De-Ping
    View author publications

    You can also search for this author in PubMed Google Scholar

Additional information

Project supported by the National Natural Science Foundation of China (59474016)

About this article

Cite this article

Wei, JH., Yu, NW., Fan, YY. et al. Study on flow and mixing characteristics of molten steel in RH and RH-KTB refining processes. J. of Shanghai Univ. 6, 167–175 (2002). https://doi.org/10.1007/s11741-002-0028-x

Download citation

  • Received:

  • Issue Date:

  • DOI: https://doi.org/10.1007/s11741-002-0028-x

Key words

Search

Navigation