Date of Award

12-1-1970

Document Type

Thesis

Degree Name

Master of Science (MS)

Department

Chemical Engineering

Abstract

Fly ash produced from burning fossil fuels presents an air pollution problem when it is discharged into the atmosphere. Fly ash can be removed from gases using electrostatic precipitation. Efficiency of precipitation depends to a large extent on the bulk electrical resistivity of the fly ash which in turn depends on conditions such as ash temperature, moisture content of the gas, and ash composition. Bulk electrical resistivity is the total resistivity of a dust layer.

A bulk electrical resistivity testing apparatus was built and operated according to the American Society of Mechanical Engineers Power Test Code 28 to investigate the resistivity characteristics of fly ashes from low-rank Western coals.

For statistical purposes, experimentation was set up in a factorial design to obtain desired information from minimum testing. The effects of the test variables were analyzed by use of variance, regression, and graphical methods.

Results showed that temperature, moisture, and chemical composition, particularly the amount of Nao0, had large effects on ash resistivity. Increasing temperature below about 300° F causes resistivity to rise, but increasing temperature above about 300° F causes resistivity to drop. Resistivity decreases as the moisture content of the gas increases. Resistivity also decreases as the sodium content of the ash increases. Size distribution had very little influence on bulk electrical resistivity.

Further testing should be done using the "in-situ" method of resistivity measurement to obtain data at the flue gas conditions actually existing in a precipitator.

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