TRACE-ELEMENT PARTITIONING DURING COAL-GASIFICATION

The fate of trace element pollutants in integrated gasification combin ed-cycle (IGCC) systems is closely tied to their volatilization in the gasifier and subsequent condensation or reaction with fine fly ash pa rticles. The results of an experimental bench-scale programme to measu re the partitioning of selected trace elements during atmospheric pres sure entrained flow gasification of Illinois No.6 bituminous coal are presented. The experimental data are used in conjunction with thermody namic equilibrium calculations to investigate the downstream behaviour of the volatile elements. It is shown that a significant mass fractio n of each of the elements As, Se, Sb, Pb and Hg vaporizes during gasif ication of this coal, whereas Cd, Cr, Co, Mn, Ni, U and Th are relativ ely non-volatile. Under the reducing conditions associated with the ga sifier product gas, As, Sb, Pb, Hg, and Se remain in the vapour phase at temperatures of 773 to 873 K, the operating range of most hot gas r emoval systems. (C) 1996 Elsevier Science Ltd.