Coal Ash Fusion Temperatures — New Characterisation Techniques, and Associations with Phase Equilibria
The well-documented shortcomings of the standard technique for estimating the fusion temperature of coal ash are its subjective nature and poor accuracy. Alternative measurements based on the shrinkage and electrical conductivity of heating samples are therefore examined with laboratory ash prepared at about 800°C in crucibles, as well as combustion ash sampled from power stations. Sensitive shrinkage measurements indicate temperatures of rapid change which correspond to the formation of liquid phases that can be identified on ternary phase diagrams. The existence and extent of formation of these phases, as quantified by the magnitude of ‘peaks’ in the test, provide alternative ash fusion temperatures. The peaks from laboratory ashes and corresponding combustion ashes derived from the same coals show clear differences which may be related to the evaporation of potassium during combustion and the reactions of the mineral residues to form combustion ash.
KeywordsFusion Temperature Iron Silicate Shrinkage Test Rapid Shrinkage Australian Coal
Unable to display preview. Download preview PDF.
- ACIRL (1993), Investigations of Slagging at Callide B Power Station. Unpublished Report to Queensland Electricity Commission.Google Scholar
- Coin, C., Reifenstein, A.P., Kahraman H. (1995), Improved Ash Fusion Test, this symposium.Google Scholar
- Couch, G. (1994), Understanding Slagging and Fouling in PF Combustion IBACR/TJ2, lEA Coal Research Laboratories, August.Google Scholar
- Ellis, G.C. (1989), The Thermomechanical, Electrical Conductance and Chemical Characteristics of Coal Ash Deposits, NERDDP Project No. 1181 Final Report Volume III, Secv R and D Dept, Australia.Google Scholar
- Huffman, P.G., Huggins F.E., Dunmyre G.R. (1981), Investigation of the High Temperature Behaviour of Coal Ash in Reducing and Oxidising Atmospheres, Fuel, 6.Q, 585–597.Google Scholar
- Juniper, L. (1995), Applicability of Ash Slagging “Indices” Revisited, Combustion News February, Australian Combustion Technology Centre. pp. 1–4.Google Scholar
- Khan, R.M. and Williford, C.A. (1989), Novel Technique for Direct Measurement of Ash Fusion and Sintering Behaviour at Elevated Temperature and Pressure - International Conference on Coal Science, Tokyo.Google Scholar
- Gibson, J.R. and Livingston, W.R. (1991), The Sintering and Fusion of Bituminous Coal Ashes, Engineering Foundation Conference on Inorganic Transformations and Ash Deposition During Combustion, Palm Coast, Florida, p425–447.Google Scholar
- Lee, G.K. et al, (1991), Assessment of Ash Sintering Potential by Conductance and Dilatometry, Pittsburgh Coal Conference.Google Scholar
- Sanyal, A. Mehta, A.K. (1994), Development of an Electrical Resistance Based. Ash Fusion Test. The Impact of Ash Deposition in Coal Fired Furnaces, p445–460, Taylor and Francis, Washington.Google Scholar
- Sanyal, A., and Cumming I.W. (1981), An Electrical Resistivity Method for Deterring the Onset of Fusion in Coal Ash, US Engineering Foundation Conference on Slagging and Fouling from Combustion Gases, Henniker, p329–341.Google Scholar
- Wall, T.F. et al, (1995), Demonstration of the True Ash Fusion. Characteristics of Australian Thermal Coals. ACARP Project C3039 Final Report (in preparation).Google Scholar