Relationship between bed thickness, average ash content, and Zn and Pb content in coal in the Upper Silesian Coal Basin

Abstract

Varying frequency of the occurrence of coal interbeds and thin, medium and thick coal beds in the paralic and the limnic coal-bearing series was determined in the Upper Silesian Coal Basin. Thin coal beds occur in the basin most frequently. Typically, the ash content and Zn and Pb content decrease with the increasing thickness of the beds. The highest ash content and content of Zn and Pb occur in thin coal beds, less than 0.3 m thick (especially in the limnic series) and thin beds of coal shales 0.3-0.7 m thick. The average ash content of coal and average content of Zn and Pb mainly reflect a content in thin beds (0.7-1.5 m in the limnic series and below 0.7 min the paralic series), most frequently occurring in the basin. Variability of Zn and Pb content is closely associated with ash-forming substances in coal. The presently varying levels of concentrations of Zn and Pb in coal beds are assumed to result from sorption-diffusion processes of coal enrichment, which involved the entire thickness in thin beds, though affected only in near-top and near-bottom parts of thick beds.