Speciation variation of trace metals in coal gasification and combustion

Abstract

Coal gasification is a very important aspect of coal use today. In this paper, the speciation of trace metals (Cu, Pb, Zn, Mo, Mn, V, Ba, and Be) in crude lignite, combustion ash and gasification ash is studied in order to understand the environmental impact of coal gasification on trace metal pollution. Results demonstrate that the trace metals are changed partly from the active (labile) fraction to the residual (non-labile) fraction in the processes of gasification and direct combustion. The metals bound to the active fraction in gasification ash are diminished in the process of lignite gasification more than in the process of lignite direct combustion: 73.1% for Cu, 86% for Pb, 74.1% for Zn, 46.3% for Mo, 35% for Mn, 29.8% for V, 1.9% for Ba, and 40.2% for Be. These facts suggest that the coal gasification is a reasonable method of coal utilization for the environment protection of trace metal pollution from coal ashes, as well as for resource economics.