Distribution of As, Hg and other trace elements in different size and density fractions of the Reshuihe high-sulfur coal, Yunnan Province, China

The genetic type and mode of occurrence of elements in coal both exert a great impact on their removability; epigenetic and coarse minerals may be readily liberated by gravity separation. Elements associated with pyrite (e.g., As, Hg, Co, Ni, Cu, Se, Sb and Tl) demonstrate high removability; F, Th, U, V and Cr, which mainly occur in clay minerals and/or organic components of the coal, show a relatively low removability. Trace elements in particle size fractions 6-13 mm and < 0.5 mm are most easily removed by gravity separation. In order to fully remove toxic elements from coal, it is suggested fractions with particle sizes of 3-6 mm and 0.5-3 mm be reduced in size to < 0.5 mm prior to gravity separation.