MINERALOGICAL SPECIATION OF ELEMENTS IN AN EASTERN CANADIAN FEED COALAND THEIR COMBUSTION RESIDUES FROM A CANADIAN POWER-PLANT

Systematic changes in mineralogy, enrichment and depletion of selected elements, and mineralogical speciation of selected elements in fly as h and bottom ash samples from the Lingan Power Plant were compared to run-of-mine and pulverized feed coal from the Sydney coalfield, Nova S cotia, eastern Canada. The analytical techniques used were an electron microprobe equipped with energy and wavelength X-ray dispersive spect rometers, X-ray diffraction, neutron activation, scanning electron mic roscopy with energy dispersive X-ray and incident light petrography. T hree types of glasses (Fe/O-rich, Fe/Al/Si/O-rich and or Al/Si/O-rich) were identified in the combustion residues; they were formed as a res ult of the interaction of melted pyrite and clay minerals. Compared to the feed coal, most elements were enriched 10 to 20 times in the fly ask The concentration of the elements in both the fly ash and bottom a sh are comparable to coal ash that is generated by the low temperature asher in the laboratory. Some chalcophile elements such as arsenic an d lead occurred as a solid solution in pyrite in the feed cod and were concentrated in the float fraction (density: < 2.81 g/cm(3)) of the f ly ash with non-crystalline Fe-oxides. X-ray mapping of arsenic in the fly ash and bottom ash indicates that arsenic was evenly distributed as oxide within the Fe/O- and Fe/Al/Si/O-rich glass and crystalline ph ases in the fly ash, possibly in solid solution. Arsenic is associated with Fe/O and Fe/S crystalline phases in the bottom ash.