Characterization of Ash Deposit Structure from Planar Sections: Results and Challenges

  • Everett R. Ramer
  • Donald V. Martello


Three-dimensional structural parameters were measured for fouling ash deposits from two Powder River Basin subbituminous coals using direct microscopical methods on planar sections through the deposits. These parameters included solid and pore volume fractions; specific surface area; particle contiguity; and mean solid, particle, and pore chord lengths. Spatial trends in the results for the two deposits indicated that the solid volume fraction remained relatively constant from the tube side to the flame side, but the solid phase coarsened in this direction. An increase in the contiguity between ash particles indicated that the coarsening mechanism was sintering, both via increased particle agglomeration and encapsulation of particles by a glassy phase. The bulk averages of the results were identical for both deposits, with a solid volume fraction of 0.23, a specific surface area of 0.6 x 106 m−1, a contiguity of 0.23, a mean solid chord length of 16 pm, a mean particle chord length of 12 µm, and a mean pore chord length of 53 µm. In addition, a two-dimensional structural parameter, the density-density correlation function, was measured for one of the deposits. This result indicated that the cross-sectional profiles of the solid regions with diameters less than 20 µm were isotropically oriented, and that the larger solid region profiles were preferentially oriented in the direction of the incoming particle trajectories.


Planar Section Chord Length Tube Surface Solid Volume Fraction Spatial Profile 
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  1. Berryman, J. G. and Blair, S. C. (1986). “Use of Digital Image Analysis to Estimate Fluid Permeability of Porous Materials: Application of Two-Point Correlation Functions.” J. AppL Phys ., 60 (6), 1930–1938.Google Scholar
  2. DeHoff, R. T. (1986). “Quantitative Microstructural Characterization and Description of Multiphase Ceramics.” in Tailoring Multiphase and Composite Ceramics, New York: Plenum Press, 207–222.Google Scholar
  3. Gurland, J. (1958). “Spatial Distribution of Discrete Particles.” in R. T. DeHoff and F. N. Rhines (eds.) Quantitative Microscopy, New York: McGraw-Hill, 278–290.Google Scholar
  4. Hurley, J. P., Benson, S. A., and Mehta, A. K. (1994). “Ash Deposition at Low Temperatures in Boilers Burning High-Calcium Coals.” in Williamson, J. and Wigley, F. (eds.) The Impact of Ash Deposition on Coal Fired Plants, Washington: Taylor and Francis, 19–30.Google Scholar
  5. Hurley, J. P., Erickson, T. A., Benson, S. A., and Brobjorg, J. N. (1991). “Ash Deposition at Low Temperatures in Boilers Firing Western U. S. Coals.” Presented at the International Joint Power Generation Conference, San Diego, California, October 7–10, 1991.Google Scholar
  6. Lange, D. A., Jennings, H. M., Shah, S. P. (1994). “Image Analysis techniques for Characterization of Pore Structure of Cement-Based Materials.” Cement and Concrete Research 24(5), 841–853.Google Scholar
  7. Lin, C. (1982). “Microgeometry I: Autocorrelation and Rock Microstructure.” Mathematical Geology, 14 (4), 343–360.Google Scholar
  8. Liu, G. (1993). “Applied Stereology in Materials Science and Engineering.” J. Microsc ., 171 (1), 57–68.Google Scholar
  9. Nowok, J. W., Benson, S. A., Jones, M. L., and Kalmanovitch, D. P. (1990). “Sintering Behaviour and Strength Development in Various Coal Ashes.” Fuel, 69, 1020 1028.Google Scholar
  10. Pfleiderer, S., Ball, D. G. A., Bailey, R. C. (1993). “AUTO: A Computer Program for the Determination of the Two-Dimensional Autocorrelation Function of Digital Images.” Computers and Geosciences 19(6), 825–829.Google Scholar
  11. Press, W. H., Flannery, B. P., Teukolsky, S. A., and Vetterling, W. T. (1988). Numerical Recipes in C The Art of Scientific Computing, Cambridge: Cambridge University Press.Google Scholar
  12. Russ, J. C. (1990). Computer Assisted Microscopy The Measurement and Analysis of Images, New York: Plenum Press.CrossRefGoogle Scholar
  13. Torquato, S. (1992). “Connection between Morphology and Effective Properties of Heterogeneous Materials.” in S. Torquato and D. Krajcinovic (Eds.) Macroscopic Behavior of Heterogeneous Materials from the Microstructure AMD-Vol. 147, New York: ASME.Google Scholar
  14. Wain, S. E., Livingston, W. R., Sanyal, A., and Williamson, J. “Thermal and Mechanical Properties of Boiler Slags of Relevance to Sootblowing.” in Benson, S. A. (Ed.) Inorganic Transformations and Ash Deposition During Combustion, New York: Engineering Foundation, 459–470.Google Scholar
  15. Wall, T. F., Bhattacharya, S. P., Zhang, D. K., Gupta, R. P., and He, X. (1993). “The Properties and Thermal Effects of Ash Deposits in Coal-Fired Furnaces ” Prog. Energy Combust Sci. 19, 487–504.Google Scholar
  16. Weibel, E. R. (1979). Stereological Methods Vol. 1 Practical Methods for Biological Morphometry. London: Academic Press.Google Scholar
  17. Weibel, E. R. (1980). Stereological Methods Vol. 2 Theoretical Foundations. London: Academic Press.Google Scholar

Copyright information

© Springer Science+Business Media New York 1996

Authors and Affiliations

  • Everett R. Ramer
    • 1
  • Donald V. Martello
    • 1
  1. 1.Pittsburgh Energy Technology CenterU. S. Department of EnergyPittsburghUSA

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