| Summary: | The theoretical development of a sequence of mathematical sub-models capable of
calculating the fouling tendency of a coal based on microscopic analysis of the coal mineral
matter is described. The sub-models interpret computer controlled-scanning electron microscope
analysis data in terms of mineral size and chemical composition distributions; follow the
transformation of these mineral property distributions during the combustion of the coal;
determine the probability of the resultant fly ash particles impacting on boiler-tube surfaces and
of their sticking upon impaction. The sub-models are probabilistic, and take account of the
particle-to-particle variation of coal mineral matter and fly ash properties by providing mean
values and variances for particle size, chemical composition and viscosity. The various sub-
models are combined into a Coal Fouling Tendency (CFT) computer code. Comparison of CFT
modeling results obtained for any coal or coal blend with those obtained for a coal whose
behavior in a given boiler plant is known, can give useful information on their relative fouling
tendencies.
The report also includes data on the deposition characteristics of five coals or coal blends,
obtained from combustion experiments in the 1-2 MW flame tunnel at MIT. The measurement
data were used for validation of the CFT calculations, and for ranking the five fuels with respect
to their fouling behavior. Similar ranking of other coals, without combustion testing, can be
based solely on results from the CFT model, and examples are given in the report.
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