CONTRIBUTION OF THE RARE EARTH-RICH TONSTEIN TO THE CHEMISTRY OF FIRE CLAY (EASTERN KENTUCKY) COAL-DERIVED FLY ASH

The Fire Clay coal is known to be relatively enriched in rare earth elements owing to the presence of a volcanic-source tonstein within the coal. Three locations of the Fire Clay coal in the Eastern Kentucky coalfield were investigated. In all three cases, the coal and rock partings were sampled and analyzed individually. In one of the latter settings, we also were able to sample the fly ash resulting from the burn of the coal. The coal profiles represent three distinct occurrences of the rare earth-rich tonstein: (1) the tonstein not present with any other rock partings, (2) the tonstein underlain by an illitic clay parting, and (3) the tonstein is not present but the coal has a high-REE concentration. Of the first two settings, the tonstein comprises about 10% of the total thickness of the coal + parting profile and contributes about 20-35% of the total rare earth elements + Yttrium (REY). For mines with preparation plants, the latter amount of REY represents material largely not shipped to power plant. For mines shipping run of mine coal and/or shipping coal from the type (3) setting, the resulting coal combustion fly ash might have 1400-1600 ppm REY. In contrast, power plants burning coal with lesser amounts of entrained REY-rich partings, the fly ash REY is about 800-900 ppm.