Pyrite decomposition interface

The extent of pyrite decomposition was followed by obtaining S/Fe atomic ratios at various points across selected pyrite inclusions, the latter in the size range 10-20 pm. Figure 1 is a plot of this ratio versus "distance from interface within pyrite for each of the coals at different temperatures. The results indicate that, for pyrite of this size, decomposition to pyrrhotite occurs in the temperature range 450-500°C, for all the coals studied. The reaction essentially was complete at 500°C. 

The incorporation of the sulphur from the decomposition of pyrite, into the surrounding coal matrix, was also followed by scanning electron microscopy. This involved spot analysis for sulphur out from the pyrite/coal interface into the surrounding matrix. These results follow the trend presented above for pyrite decomposition. At 400 and 450°C, little sulphur transfer was observed at 500however, there was an observed increase in the J sulphur (Fig. 5), in the region around the decomposed particle. 

---