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Show Experiments to determine the form of the element chromium in coal and ash were also conducted. Chromium in the + 6 oxidation state is more hazardous as it is a known carcinogen. Using X A F S spectroscopy, the forms of chromium in an Illinois #6 parent coal, a physically beneficiated Illinois #6 coal (SOAP), and their respective combustion derived ashes were examined. As shown in Figures 5 and 6, chromium was present in the +6 oxidation state in all cases. Details of this study are described elsewhere (11). Gasification Study Size-segregated samples generated during atmospheric pressure entrained gasification of an Illinois #6 coal were analyzed by N A A and PIXE. These samples were size-segregated during collection into samples with median cut diameters of approximately 10, 4, 0.3, and < 0.3 /xm. N A A results indicated enrichment of certain trace elements in the smaller particle size fractions examined. Arsenic and selenium concentrations in the smallest particle size fraction were 25-30 ppm, a factor of ten enrichment relative to the 2-3 p p m in the largest size fraction. Antimony concentrations of approximately 10 p p m were observed in the smallest particles v. 0.5 p p m in the largest, again indicative of enrichment. In contrast, chromium and cobalt concentrations in the smallest particles were an order of magnitude smaller than concentrations in the largest particles. Cadmium showed no trend with particle size, with concentrations in all samples of 0.4 - 2 p p m observed. As indicated by PIXE, lead concentrations also increased with decreasing particle size, form 330 p p m in 1 itm particles to > 1000 p p m in < 0.3 itm particles. Results are summarized in Table 4. Increasing elemental concentration with decreasing particle size is indicative of elemental volatility during gasification. W e conclude that the elements As, Se, Pb, and Sb are volatile during gasification of Illinois #6; and that Cd, Cr, and C o are non-volatile. The behavior of Cr and C o is suggestive of their association with larger minerals that are not collected on the lower stages of the impactor (smaller particle sizes). Trace Element Capture Experiments Limited experiments were also conducted to determine the oxidation state of arsenic and chromium that have condensed from the vapor phase. Using the reactor shown in Figure 2, arsenic powder and chromium 2,4 pentanedionate were vaporized at 300°C in 1 0 % oxygen in nitrogen. After heating the vapors to 1000°C to more closely approximate combustion conditions, a fume was generated by gas quenching. The condensed samples were then analyzed by x-ray diffraction. As203 and Cr203 were the only species observed. The experiments were repeated in the presence of 200 ppm of S02; again, only these two oxides were observed. The ability of sorbents to capture selected trace metal vapors was demonstrated in a second series of experiments. Water soluble chlorides of lead and nickel, and water-soluble oxides of arsenic and chromium (VI) were mixed with magnesia and diatomaceous earth sorbents at a mass ratio of 15/1 sorbent/metal and pelletized. Pellets were then heated to 4 11-14 |