Conclusions
The traditional measurement of the temperatures of fusibility of coal ash, which are called ash fusibility temperatures (AFT), are shown in correspond to the existence of more than 60% of melt phase in the samples. These temperatures do not appear to correspond to the ash melting characteristics often associated with them. It was found that the deformation temperature is not the temperature at which initial melting begins as normally perceived and the hemisphere temperature is below the liquidus temperature.
A new technique—Thermomechanical Analysis (TMA)—measures the progressive shrinkage of ash and is shown to be capable of characterising the sintering and melting behaviour at temperatures lower than the traditional technique. Shrinkage temperatures may be defined which corresponding to particular shrinkage levels are denoted as TS% (for S of 25%, 50%, 75% and 90%), and these are proposed as alternatives to the existing ash fusibility temperatures. The new temperatures are measured with much better accuracy (±10°C) than the traditional temperatures (±40°C) and are suggested as indicators of initial melting (25%), intermediate melting (60%), completion of melting (80%) and slag flow characteristics.
Correlation between the alternative shrinkage temperatures, the traditional ash fusibility temperatures and the measured extents of melting indicated that the shrinkage temperatures provide an improved and objective method of quantifying the various stages of melting. The correlation of the extent of melting with the extent of sticky particles and slag viscosity will allow the application of the new shrinkage temperatures to characterise ash effects in combustion systems.
This is a preview of subscription content, log in via an institution to check access.
Access this chapter
Tax calculation will be finalised at checkout
Purchases are for personal use only
Preview
Unable to display preview. Download preview PDF.
References
Barret, R. E. (1987). “Slagging and fouling in pulverised-coal-fired utility boilers—Volume 2: A survey of boiler design practices for avoiding slagging and fouling”, EPRI Report CS-5523.
Bryers, R. W. (1996). “Fireside slagging, fouling and high temperature corrosion of heat transfer surface due to impurities in steam raising fuels”, Progress in Energy Combust. Science, Vol. 22, pp. 29–120.
Ellis, G. C. and Ledger, R. C. (1989). “The Thermomechanical, electrical conductance and chemical characteristics of coal ash deposits”, In “SECV (R&D) Report SO/89/164, NERDDP Project No. 1181, SECV Project No. 2411, Australia.
Ely, F. G. and Barnhart, D. H. (1963). In: H. H. Lowry (Ed.), Chemistry of coal utilisation, Supplementary volume, Wiley, New York, p. 820.
Huggins, F. E., Kosmack, D. A. and Huffman, G. P. (1981). “Correlation between ash-fusion temperatures and ternary equilibrium phase diagrams”, Fuel, 60, 577–584.
Huffman, G. P., Huggins, F. E. and Dunmyre, G. R. (1981). “Investigation of the high-temperature behaviour of coal ash in reducing and oxidizing atmospheres”, Fuel, 60, 585–597.
Juniper, L. (1995). “Applicability of ash slagging “Indices” Revisited”, Australian Combustion Technology Centre, February, Combustion News p. 1–4.
Kalmanovitch, D. P. and Williamson, J. (1986). “Crystallization of coal ash melts”, In Karl Vorres (Ed.), Mineral Matter and Ash in Coal, ACS Symposium series 301, August, 1984, pp. 234–255.
Levin, E. M., McMurdie, H. F. and Hall, H. P. (1964), “Phase Diagrams for Ceramists” Am. Ceramic. Soc., Inc., Columbus, Ohio and references therein.
Raask, E. (1979). “Sintering characteristics of coal ashes by simultaneous dilatometry-electrical conductance measurements”, Thermal Analysis, 16, p. 91.
Raask, E. (1986). “Flame vitrification and sintering characteristics of silicate ash”, In “Mineral Matter and Ash in Coal”, ACS Symposium series 301, in (Ed. Karl Vorres), p. 139.
Sanyal, A. and Mehta, A. K. (1994). “Development of an electrical resistance based ash fusion test”, In Williamson, J. and Wigley, F. (Ed.), The Impact of Ash Deposition in Coal Fired Furnaces, Taylor and Francis, Washington, p. 445.
Saxby, J. D. and Chatfield, S. P. (1996). “Fusion of coal ash by thermo-mechanical analysis”, Proceedings of the 7th Australian Coal Science Conference, Australian Institute of Energy, p. 391, Australia.
Vassilev, S. V., Kitano, K., Takeda, S. and Tsure, Tl. (1995). “Influence of mineral and chemical composition of coal ashes on their fusibility”, Fuel Processing Technology, Vol. 45 pp. 27–51.
Wall, T. F, Creelman R. A., Gupta, R. P., Gupta, S. K, Sanders, R. H. and Lowe, A. (1995), “Demonstration of the true ash fusion characteristics of Australian thermal coals”, ACARP Project Final Report C3093, Australia.
Author information
Authors and Affiliations
Editor information
Editors and Affiliations
Rights and permissions
Copyright information
© 2002 Kluwer Academic Publishers
About this chapter
Cite this chapter
Gupta, S.K., Gupta, R.P., Bryant, G.W., Juniper, L., Wall, T.F. (2002). Thermomechanical Analysis and Alternative Ash Fusibility Temperatures. In: Gupta, R.P., Wall, T.F., Baxter, L. (eds) Impact of Mineral Impurities in Solid Fuel Combustion. Springer, Boston, MA. https://doi.org/10.1007/0-306-46920-0_10
Download citation
DOI: https://doi.org/10.1007/0-306-46920-0_10
Publisher Name: Springer, Boston, MA
Print ISBN: 978-0-306-46126-2
Online ISBN: 978-0-306-46920-6
eBook Packages: Springer Book Archive