TRACE-ELEMENTS IN COAL AND THEIR BEHAVIOR DURING COMBUSTION IN A LARGE POWER-STATION

The trace elements (As, B, Ba, Be, Bi, Cd, Co, Cr, Cs, Cu, Ga, Ge, Hg, Li, Mn, Mo, Ni, Pb, Rb, Sb, Se, Sn, Sr, Ta, Th, Tl, U, V, W, Y, Zn, Z r and REE) in a subbituminous coal and their behaviour during combusti on in a large power station were characterized by their content and di stribution in the fuel (organic and/or inorganic affinities) and in th e combustion wastes (partition and volatility). Samples were fractiona ted by density and magnetic separations and cascade impactors. Quantit ative analyses were performed by X-ray diffraction, ICP-MS, ICP-AES, A AS and ICP-AES with hydride generation. Among the findings is the impo rtant role of anhydrite (CaSO4) in the sorption of trace elements such as As, B, Ge, Se, Pb, Mo, Zn and Tl from flue gas and in the reductio n of emissions of these potentially toxic elements. Calcium oxide has a high sorption capacity for some of the elements studied. This sorpti on phenomenon and the condensation, mainly as fine fly ash particles, of important fractions of the trace elements during the cooling of flu e gas significantly reduce the gaseous emissions of potentially toxic trace elements from coal combustion in the power station studied.