Volatility and chemistry of trace elements in a coal combustor

The volatility of 16 trace elements (TEs) (As, Cd, Co, Cr, Cu, Hg, Mn, Ni, Pb, Sb, Se, Sn, Te, TI, V, Zn) during coal combustion has been studied depe nding on the combustion conditions (reducing or oxidizing) and type of coal (high- or low-ash coal), together with their affinities for several active gaseous atoms: Cl, F, H, O, and S. The elements can be divided into three groups according to their tendencies to appear either in the flue gases or in the fly ashes from a coal combust or: Group 1: Hg and Tl, which are volatile and emitted almost totally in the va por phase. Group 2: As, Cd, Cu, Ph and Zn, which are vaporized at intermediate tempera ture and are emitted mostly in fly ashes. Group 3: Co, Cr, Mn and V, which are hardly vaporized and so are equally di stributed between bottom ashes and fly ashes. In addition, Sb, Sn, Se and T e may be located between Groups 1 and 2, and Ni between 2 and 3. At 400 and 1200 K, the 16 TEs behave differently in competitive reactions w ith Cl, F, H, O and S in a coal combustor. (C) 2001 Elsevier Science Ltd. A ll rights reserved.