Research Papers: Gas Turbines: Coal, Biomass, and Alternative Fuels

Deposition of Corrosive Alkali Salt Vapors on the Blades of Gas Turbines Fueled by Coal-Derived Syngases

[+] Author and Article Information
John B. Young

Hopkinson Laboratory,
Cambridge University Engineering Department,
Cambridge CB2 1PZ, UK
e-mail: jby@eng.cam.ac.uk

Richard J. Tabberer

E.ON UK plc,
Westwood Way,
Coventry CV4 8LG, UK

John E. Fackrell

Technology Centre,
E.ON New Build & Technology Ltd.,
Nottinghamshire NG11 0EE, UK

1Corresponding author.


Contributed by the Coal, Biomass and Alternate Fuels Committee of ASME for publication in the Journal of Engineering for Gas Turbines and Power. Manuscript received March 25, 2013; final manuscript received June 12, 2013; published online August 21, 2013. Assoc. Editor: Paolo Chiesa.

J. Eng. Gas Turbines Power 135(9), 091401 (Aug 21, 2013) (13 pages) Paper No: GTP-13-1088; doi: 10.1115/1.4024948 History: Received March 25, 2013; Revised June 12, 2013

Many proposed clean coal technologies for power generation couple a gasification process with a gas turbine combined cycle unit. In the gasifier, the coal is converted into a syngas which is then cleaned and fired before entering the turbine. A problem is that coal-derived syngases may contain alkali metal impurities that combine with the sulfur and chlorine from the coal to form salts that deposit on the turbine blades, causing corrosion. This paper describes a new model, applicable to most types of coal, for predicting the dewpoint temperatures and deposition rates of these sodium and potassium salts. When chlorine is present the main alkali species in the mainstream gas flow are the chlorides; but when chlorine is absent, the superoxides dominate. However, because the high-pressure turbine blades are film-cooled, they are at much lower temperatures than the mainstream gas flow and analysis then shows that the deposit is composed almost entirely of the sulfates in either liquid or solid form. This is true whether or not chlorine is present. Detailed calculations using the new model to predict the alkali salt deposition rates on three stages of an example utility turbine are presented. The calculations show how the dewpoint temperatures and deposition rates vary with the gas-phase chlorine and sulfur levels as well as with the concentrations of sodium and potassium. It is shown that the locations where corrosion is to be expected vary considerably with the type of coal and the levels of impurities present.

Copyright © 2013 by ASME
Your Session has timed out. Please sign back in to continue.


Minchener, A. J., 2005, “Coal Gasification for Advanced Power Generation,” Fuel, 84, pp. 2222–2235. [CrossRef]
Kunze, C., and Spliethoff, H., 2010, “Modelling of an IGCC Plant With Carbon Capture for 2020,” Fuel Process. Technol., 91, pp. 934–941. [CrossRef]
Fujii, T., 2007, “Deployment of IGCC Technology With Carbon Capture,” Proceedings of the 6th Annual Conference on Carbon Capture and Sequestration, Pittsburgh, PA, May, 2007.
Spacil, H. S., and Luthra, K. L., 1982, “Volatalization/Condensation of Alkali Salts in a Pressurized Fluidized Bed Coal Combustor/Gas Turbine Combined Cycle,” J. Electrochem. Soc., 129, pp. 2119–2126. [CrossRef]
Molière, M., and Sire, J., 1993, “Heavy Duty Gas Turbines Experience With Ash Forming Fuels,” J. Phys. Colloq., 3, pp. 719–730.
Wolf, K. J., Müller, M., Hilpert, K., and Singheiser, L., 2004, “Alkali Sorption in Second-Generation Pressurized Fluidized-Bed Combustion,” Energy Fuels, 18, pp. 1841–1850. [CrossRef]
Fackrell, J. E., Tabberer, R. J., Young, J. B., and Fantom, I. R., 1994, “Modelling Alkali Salt Vapour Deposition in the British Coal Topping Cycle System,” Proceedings of the ASME Gas Turbine and Aeroengine Congress, The Hague, The Netherlands, June 13–16, Paper No. 94-GT-177.
Clark, R. K., Arnold, M., Fackrell, J. E., Mordecai, M., and Dawes, S. G., 1991, “The Grimethorpe Topping Cycle Project,” FBC Technology and the Environmental Challenge, Adam Hilger, Bristol, UK, pp. 353–362.
Rosner, D. E., Chen, B.-K., Fryburg, G. C., and Kohl, F. J., 1979, “Chemically Frozen Multi-Component Boundary Layer Theory of Salt and/or Ash Deposition Rates From Combustion Gases,” Combust. Sci. Technol., 20, pp. 87–106. [CrossRef]
Scandrett, L. A., and Clift, R., 1984, “The Thermodynamics of Alkali Removal From Coal-Derived Gases,” J. Inst. Energy, 57, pp. 391–397.
Chase, M. W., Jr., National Institute of Standards and Technology (U.S.), 1998, NIST-JANAF Thermochemical Tables, 4th ed., American Chemical Society, Washington, DC.
Dessureault, Y., Sangster, J., and Pelton, A. D., 1990, “Coupled Phase Diagram and Thermodynamic Analysis of the Nine Common-Ion Binary Systems Involving the Carbonates and Sulphates of Lithium, Sodium and Potassium,” J. Electrochem. Soc., 137, pp. 2941–2950. [CrossRef]
Crawford, M. E., and Kays, W. M., 1976, “STAN5—A Program for Numerical Computation of Two-Dimensional Internal and External Boundary Layer Flows,” NASA Report No. CR-2742.
Wilke, C. R., 1950, “Diffusional Properties of Multicomponent Gases,” Chem. Eng. Prog., 46, pp. 95–104.
Poling, B. E., Prausnitz, J. M., and O'Connell, J. P., 2001, The Properties of Gases and Liquids, 5th ed., McGraw-Hill, New York, Chap. 11.


Grahic Jump Location
Fig. 1

Layout diagram of the proposed MHI 250 MW coal gasification combined cycle plant

Grahic Jump Location
Fig. 2

Variations with reciprocal temperature of the gas-phase equilibrium constants for the chemical equilibria of Eqs. (1)–(3), calculated from Eq. (A2)

Grahic Jump Location
Fig. 3

Partitioning of the alkali species in the mainstream flow of a hypothetical turbine expansion from 1800 K and 15 bar with polytropic efficiency 0.9. Full equilibrium calculations based on XO2 = XH2O = 0.1, XSO2 = 10-4, XNa = XK = 4×10-8; (a) chlorine free coal with XHCl = 0, (b) high chlorine coal with XHCl = 10−4.

Grahic Jump Location
Fig. 4

Saturated vapor pressures for (a) Na2SO4 and NaCl, and (b) K2SO4 and KCl, calculated from Eq. (C2). The SVP over liquid has been extended below the melting temperature into the supercooled region.

Grahic Jump Location
Fig. 5

Variation with mole fraction of the activity coefficients for mixtures of Na2SO4 and K2SO4 calculated from Eqs. (D2) at three temperatures; (a) liquid solution, (b) solid solution

Grahic Jump Location
Fig. 6

Computed equilibrium phase diagram for a mixture of Na2SO4 and K2SO4 together with a compilation of experimental data points from Dessureault et al. [9]

Grahic Jump Location
Fig. 7

Variation with temperature of the mole fraction of MCl in a liquid or solid mixture of M2SO4 and MCl. Calculations based on XO2 = XH2O = 0.1, XSO2 = XHCl = 10-4, γMSu = γMCl = 1, and p = 10 bar.

Grahic Jump Location
Fig. 8

High chlorine coal. Deposition rates at the leading edges of the first three stages of the example turbine as a function of blade surface temperature: (a) original model without superoxides, (b) new model with superoxides.

Grahic Jump Location
Fig. 9

Flow calculations for the first stage stator of the example turbine: (a) velocity distribution outside the boundary layer, (b) surface temperature distribution

Grahic Jump Location
Fig. 10

High chlorine coal. Deposition rates on the first stage stator of the example turbine: (a) original model without superoxides, (b) new model with superoxides.

Grahic Jump Location
Fig. 11

Low chlorine coal. Deposition rates on the leading edges of the first three stages of the example turbine as a function of blade surface temperature: new model with superoxides.

Grahic Jump Location
Fig. 12

Low chlorine coal. Deposition rates on the first stage stator of the example turbine: new model with superoxides.

Grahic Jump Location
Fig. 13

First stage stator leading edge deposition rates for varying chlorine levels

Grahic Jump Location
Fig. 14

First stage stator leading edge deposition rates for varying sulfur levels

Grahic Jump Location
Fig. 15

First stage stator leading edge deposition rates for varying alkali salt levels: (a) 0 ppmv HCl, (b) 300 ppmv HCl



Some tools below are only available to our subscribers or users with an online account.

Related Content

Customize your page view by dragging and repositioning the boxes below.

Related Journal Articles
Related eBook Content
Topic Collections

Sorry! You do not have access to this content. For assistance or to subscribe, please contact us:

  • TELEPHONE: 1-800-843-2763 (Toll-free in the USA)
  • EMAIL: asmedigitalcollection@asme.org
Sign In