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Deposition and Blade Fouling of Gas Turbines by Fuel Impurities and Additives

  • J. W. Laxton
  • C. G. Stevens
  • D. Tidy

Abstract

CEGB gas turbines at present burn distillate fuel-oil and there would thus be an advantage in terms of fuel cost, if a less-refined fuel such as crude or residual fuel oil could be used. Compounds of sodium and vanadium which occur in such fuels, however, deposit on the blades and corrode them. This effect can be minimized by adding magnesium and silicon compounds to the fuel but these then become a major source of blade fouling the deposit is, however, less adherent and can be fairly readily removed. The present work was concerned with an experimental study of these effects.

The experiments were made in a high pressure combustor simulating a gas turbine environment. Sodium, vanadium, magnesium and silicon were normally added to the gas oil fuel as oil soluble compounds but in some tests magnesium was added as a suspension. The combustor itself was a modified form of the type used in the Rolls Royce Tyne engine. Deposition rates were measured on test surfaces simulating gas turbine blades at 1060 K and 1160 K (gas temperature 1080 K and 1180 K) at pressures and gas velocities typical of those used in current industrial gas turbines. They were found to compare quite closely with fouling rates reported for operational engines burning dirty fuels.

One conclusion drawn from the deposition data is that vanadium is deposited as particulate tetroxide, V2O4, which is then slowly oxidized to V2O5 which can then evaporate. The presence of sodium or magnesium in deposits, or a high carbon burden in the combustion gas, reduces the evaporation of deposited vanadium and, as a consequence, the amounts of vanadium in the deposit increases. On the other hand the apparent rate of deposition of sodium compounds was depressed by vanadium in the fuel. A possible explanation for this is offered in terms of the reduction of sodium sulphate within the deposit to the more volatile hydroxide by particles of depositing V204, i.e. Na2SO4 + V2O4 + H2O → V2O5↑ + 2Na0H↑ + S02.

In other experiments when magnesium and vanadium were added to the fuel the total rate of deposition was constant and proportional to the impurity concentration in the fuel up to deposit weights of 60gm−2. The overall deposition rate, when expressed as oxides in the deposit, approximated to 4×10−3gm−2 per w.p.p.m. of the elements in the fuel per hour of exposure. This suggests that blade cleaning would be needed at intervals of104 and 500h when burning crude and residual fuel oils, respectively, to maintain turbine efficiency within 90 to 95% of that for cleaned blades. The rate of fouling by Mg or Mg and V together was increased with sodium in the fuel but the addition of silicon to the fuel resulted in reduced fouling by Mg + V on Mg + V + Na.

Keywords

Vanadium Pentoxide ASME Paper Vanadium Concentration Deposit Weight Fouling Rate 
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. Bammert, K. and Stobbe, H., 1970, 1970, ASME Paper 70-WA/GT-4.Google Scholar
  2. Bammert, K. and Sandstede, H., 1972, ASME Paper 72-GT-34.Google Scholar
  3. Bammert, K. and Sandstede, H., 1975, ASME Paper 75-GT-35.Google Scholar
  4. Bammert, K. and Sandstede, H., 1976, ASME Paper 76-GT-66.Google Scholar
  5. De Greef, J.L., Maes, P. and Johnson, K.W., 1978, ASME Paper 78-GT-104.Google Scholar
  6. Felix, P., 1977, Brown Boveri Rev., 64 (1), 40–46.Google Scholar
  7. Felix, P., 1978, ASME Paper 78-GT-103.Google Scholar
  8. Friedlander, A.J., Felix, P. and Hess, H.J., 1974, ASME Paper 74-GT-12.Google Scholar
  9. General Electric, 1973, Gas Turbine World, 3 (4), 30–33.Google Scholar
  10. Halstead, W.D., 1973, Deposition and Corrosion in Gas Turbines, Ed. A.B. Hart, A.J.B. Cutler, 22 - 33. Applied Science Publishers, London.Google Scholar
  11. Laxton, J.W., Stevens, C.G. and Tidy, D., 1978, European Concerted Action, COST 50 Materials for Gas Turbines UK/6. Final Report (Part I ).Google Scholar
  12. Lee, S.Y., Young, W.E. and Vermes, G., 1973, ASME Paper 73-GT-l.Google Scholar
  13. Matthews, D., 1956, Ph.D. Thesis, Birmingham, U.K.Google Scholar
  14. May, W.R., Zetlmeisl, M.J. and Annard, R.R., 1973, ASME Paper 73-WA/CD-l.Google Scholar
  15. May, W.R., Zetlmeisl, M.H. and Annard, R.R., 1975, ASME Paper 75-WA/CD-5.Google Scholar
  16. Polyakov, A.Y., 1946, J. Phys. Chem., USSR, 20, 1021.Google Scholar
  17. Pegg, 1964, Referred to in BP Literature Survey on Fire-side Corrosion and Deposits by Edwards, C.J.A., BP Research Centre, Sunbury, 1964.Google Scholar
  18. Semenov, G.A., Franceva, K.E. and Shalkova, E.K., 1970, Leningrad Univ. Fiz. Khim., (3), 83–6 ( Chem. Abs., 1974, 34934A ).Google Scholar
  19. Spalding, D.B., 1963, ‘Convective Mass Transfer’, Edward Arnold, London.Google Scholar
  20. Stevens, C.G. and Tidy, D., 1981, Journal of Inst, of Energy, 3–11.Google Scholar
  21. Stevens, C.G. and Tidy, D., 1982, J. Inst, of Energy, to be published.Google Scholar
  22. Suito, H. and Gaskell, D.R., 1975, “Metal-Slag-Gas Reactions and Processes”, Ed. Foroulis, Z.A. and Smeltzer, W.W., Electrochem. Soc., Princeton, New Yersey.Google Scholar
  23. Vermes, G., 1978, ASME Paper 78-WA/GT-l.Google Scholar
  24. Zoschak, R.J. and Bryers, R.W., 1960, J. Eng. for Power, 169–180.Google Scholar

Copyright information

© ECSC, EEC, EAEC, Brussels and Luxembourg 1982

Authors and Affiliations

  • J. W. Laxton
    • 1
  • C. G. Stevens
    • 1
  • D. Tidy
    • 1
  1. 1.Central Electricity Research LaboratoriesCentral Electricity Generating BoardLeatherhead, SurreyUK

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