Trace elements in coal and their dispersal during combustion

Abstract

This is partly a review and partly the results of some experimental work. Results for concentrations of trace elements in samples of coal from 9 mines in about 100 km of one seam show the variability in terms of variance ratios, namely, maximum divided by minimum values. The dispersal of trace elements during combustion is dealt with in detail, the stress being on the fate of trace elements in stack emissions and in residues (flyash and bottom ash). Results of a 4 yr investigation of the deposition of trace elements in the environs of an Australian power plant showed decreasing amounts with distance from the stack and variations at different locations with time. In general, the amounts of trace elements collected were mostly less than the amounts contributed by rock weathering, litter decay and fertilisers. Results are given for the use of germanium to indicate the variations in proportions of flyash in deposition. It is proposed that more information should be obtained for trace elements in deposition and for the leachability of residues at particular power plants. A positive approach to environmental aspects of trace elements in coal is espoused and it is considered unlikely that harmful effects should arise from trace elements in coal if proper care is taken.