A Technique for Predicting Fly Ash Resistivity

摘要

The report gives results of research to develop a technique for predicting: the electrical resistivity of fly ash from as-received, ultimate coal analysis; and the chemical composition of the concomitant coal ash produced by simple laboratory ignition. Important chemical factors are the alkali metals, alkaline earths, and iron (with respect to the fly ash), and the water and sulfur trioxide concentrations in the flue gas. Many fly ash samples were evaluated to minimize variations due to physical effects. The effects of fly ash chemical composition, ash layer field strength, and the water and sulfur trioxide concentrations in the test environment were evaluated with respect to electrical resistivity and the evaluated parameters for the entire temperature spectrum of interest. Equipment and techniques were developed to obtain the required data. Predicted sensitivity as a function of temperature was favorably proof-tested using data acquired from previous field evaluations of precipitators at six power generating stations. The proof test involved a comparison of predicted resistivity, laboratory measured resistivity, resistivity measured in situ, precipitator efficiency, and current density of the precipitator outlet fields.