TRACE ELEMENTS IN COAL AND THEIR DISTRIBUTION CHARACTERISTICS DURING COAL COMBUSTION

Up to 36 elements in thermal coals (15 Chinese and 6 Canadian) and their corresponding ashes were determined by INAA using the SLOWPOKE-2 reactor of the University of Toronto, Canada.The concentration and distribution of trace elements in coals and their combustion products (ash and volatile matter) are presented in this paper. The results show wide variations in trace impurity concentrations (up to a factor of 100 or more) among the coals studied with few great differences between those of the Chinese and Canadian origins except that REEs, Sc, Th, U, I and Se are much higher in the former coals. For the trace element enrichment factors (EF) based on crustal abundance in coal, it has been found that only a few elements are appreciably enriched such as As (EF of 12.7), Br (5.66), I (16.4), S (230), Sb (11.4) and Se (320). During static ashing at 750℃, most of the halogens (Cl, Br and I), S and Se were volatilized whereas most other components were concentrated in ash by concentration ratios (ash/coal) r