An on-line microwave-based monitor of carbon in fly ash
Date
1997
Authors
Geisthardt, Paul Gerard
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Advisor
Brown, Robert C.
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Abstract
The amount of carbon in fly ash reveals much information about coal combustion efficiency and the quality of fly ash as a marketable product. The current standard for measuring the amount of carbon in fly ash is the manual lesson-ignition (LOI) test. The goal of this research is to increase the strength of the photoacoustic signal by changing the sampling technique and the microwave radiation source while maintaining a signal that is independent of particle size and maintaining them correlation between signal strength and carbon content of fly ash. The sampling technique was changed from isokinetic sampling to cyclonic concentration of fly ash, which results in a higher concentration of fly ash moving through the photoacoustic cell, to a closed loop fly ash handling system that simulates the flow of fly ash from cyclonic concentration. The microwave source was changed from a 600 W modified microwave oven (f =2.45 GHz), to a tunable solid-state microwave generator, this was done to eliminate problems experienced with the modified microwave oven of modulation frequency drift and power fluctuations. It is important to maintain a signal that is independent of particle size because changing conditions in the combustor bed can result in fluctuations in fly ash particle size. Maintaining the correlation between signal strength and carbon content of fly ash is the ultimate goal of this research.
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thesis