THE MICROSCOPIC NATURE OF COAL FLY-ASH PARTICLES INVESTIGATED BY MEANS OF NUCLEAR MICROSCOPY

Individual fly ash particles collected at the outlet of a pilot electr ostatic precipitator of a coal-fired power plant have been analysed by a proton microprobe. Major and trace element concentrations have been obtained for about one hundred particles in the 0.5-5 mu m size range . As a result of the combustion of the different components of the min eral matter in the parent coal, particles can be grouped in seven clas ses showing characteristic matrix compositions and different trace ele ment concentrations. The relative abundances of these groups seem to h ave a size dependence. Trace elements are found to be non-uniformly di stributed over all particles: a size dependence as well as some prefer ential association with the particle matrix have been found. Enriched concentrations of potentially toxic elements exist on smaller, most re spirable particles examined in this study, Possible reasons for this a re suggested.