Systematic Investigation of the Compositional Variations in Solid Waste Products from Coal Combustion: ABSTRACT

Abstract

A systematic study of the chemical and physical characteristics of feed coal, fly ash, bottom ash, feed limestone, and flue gas desulfurization sludge has been initiated at a Kentucky power plant. Two units at the power plant are sampled monthly for a two-year period. One unit bums a high-sulfur coal (3 wt % total S); the other unit burns a low-sulfur coal (<1 wt % total S). One focus of the study is to evaluate the variability in feed coal compositions and resulting variability in the composition of combustion solids. Major, minor, and trace element composition and mineralogy are determined on most samples. In addition, modes of occurrence, magnetic properties, stable and radiogenic isotopic composition, organic chemistry, and leachability under different conditions are determined on selected samples. Mass balance calculations show that most elements (data for Hg are not available) are retained in the solid waste products except for Se. The ratios of trace elements in the fly ash to bottom ash for both units are very similar to the order of element volatility reported in the literature. Ni, Cr, and Co show substantial enrichment in the magnetic fraction of the fly ash from the low-sulfur unit. Laboratory leaching ofmore » the fly ash and bottom ash shows that the magnetic particles are very rapidly dissolved by mild acids. Fission track results indicate that U is uniformly distributed within some fly ash cenospheres. Dark, iron-rich glass may have higher concentrations of U than does clear glass. The distribution of As appears to be uniform at low levels in most fly ash particles.« less