ANALYSIS OF BROWN COAL FLY-ASH USING X-RAY PHOTOELECTRON-SPECTROSCOPY

The surface chemical composition of brown coal #1 ash particles formed during combustion has been determined using the surface-sensitive technique of X-ray photoelectron spectroscopy (XPS). Samples taken from furnace heat exchanger tube surfaces were in both powder and aggregate form. Other samples were obtained directly using 1 cm2 steel coupons on a sample holder designed for insertion into flue gases in an experimental furnace. This allowed comparison of the XPS analyses between the fly-ash samples so acquired. After initial XPS characterization, samples were subjected to rare-gas ion (Ar+) sputtering for depth profiling purposes. The XPS technique was thus used to detect any sputter-induced composition changes or to observe any difference between the surface and bulk compositions of the ash. It was also observed that certain steels used for heat exchanger piping may well be pre-disposed to aluminosilicate fouling due to their intrinsic Al content.