This study describes the partitioning of 16 harmful trace elements (TEs; As, Cd, Co, Cr, Cu, Mg, Mn, Ni, Pb, Sb. SE, Sn, Te. Tl, V, Zn) in the flue gases from burning coal at different temperatures (300-1800 R), with various atmospheres (oxidizing or reducing conditions) and types of coal (high- or low-ash coal). Interactions between 54 chemical elements and 3200 compounds are considered in one of the mere complex thermodynamic systems so far. The 16 TEs may he classified chemically into two groups according to their dominant species at low, intermediate and high temperatures, and to their various interactions. In all, 45 major species of the 16 TEs are identified, corresponding to two major kinds of interaction: 1) combination with oxygen; 2) combination with a metal. In the temperature range 400 to 1200 S thermodynamic calculations show that the 16 TEs behave differently in competitive reactions with O, Cl, F, H, and S in a coal combustor.