Petrological Characteristics and Trace Element Partitioning of Gasification Residues from Slagging Entrained-Flow Gasifiers in Ningdong, China

Abstract

In order to better understand the petrological characteristics of gasification residues and trace element partitioning during entrained-flow gasification processes, oil-immersion microscopy, X-ray diffraction, scanning electron microscopy combined with an energy dispersive detector, inductively coupled plasma mass spectrometry, a Milestone DMA-80 Hg analyzer, and pyrohydrolysis in conjunction with a fluorine ion-selective electrode were employed to study samples collected from three commercial-scale slagging entrained-flow gasifiers in Ningdong, China. Petrological analysis indicated that dominant organic components in the residues were inertiods, fusinoids, tenuinetworks, and crassisnetworks. In addition, vitroplast and cenosphere were observed in coarse residues produced from water–slurry coal gasification. The main inorganic components were quartz, calcite, spinel, and a large amount of Al–Si glass. After gasification, most trace elements were significantly enriched in the residues. Critical trace elements Li, Be, Sc, V, Cr, Sr, REEs, Th, Nb, Ta, Zr, and Hf were enriched in the coarse residues. Critical trace elements Zn, Sb, Pb, and Bi were enriched in the fine residues, which was in accord with volatilization–condensation mechanism. The partitioning of trace elements was elucidated on the basis of their relative enrichment. Fluorine showed various partitioning behavior in three gasification processes. Mercury was the most volatile element. Generally, trace elements from the GE gasification process were less volatile; elements from the opposed four-burner gasification were more volatile; and the volatile behavior of trace elements from the Gaskombimat Schwarze Pumpe gasifier was intermediate.