Ashes Qualified as a Source of Selected Critical Elements (REY, Co, Ga, V)

The subject of the research involved fly ashes from several power plants in Poland, produced in the process of hard coal and lignite combustion. The objective of this article was to determine the concentration and distribution of elements strategic for the EU economy in ashes and in their two finest grain classes (below 20 µm and 45 µm). The differences in grain size of these ashes, as shown by granulometric tests, were significant. The concentrations of elements in the ashes and in grain classes were compared with the world average (Clarke value) for this raw material. For the majority of critical elements, a dependence of the concentration on the size of ash particles was observed. The content of REY (Rare earth elements and yttrium) and other critical elements in hard coal ashes increases with decreasing particle size. Despite the increase in the concentration of REY in the class below 20 µm, the Clarke value of these elements was not exceeded. Pearson’s correlation coefficients confirmed the interdependence between some elements of the ashes. The distribution of trace elements in grain classes of the ash was determined on the basis of observations using a scanning electron microscope equipped with an EDS (Energy Dispersive Spectroscopy) detector. Components of fly ashes that can be treated as an alternative source of strategic elements for the European Union were indicated.