IRON SULFIDE DEPOSITION DURING COAL-GASIFICATION

Previous analysis of ash generated during coal gasification using a hi gh calcium coal (SUFCo) suggested that iron sulfide was the dominant s ulfide species in the system. During a recent analysis of ash material removed from a gasification pilot unit using Pittsburgh No. 8, a high iron coal, sub-mu m to 5 mu m euhedral iron sulfide crystals were ide ntified on the outer surface of the ash. X-ray diffraction suggests bo th pyrrhotite and troilite were present in the ash. No other sulfides were identified. Within the iron sulfide crystals were siliceous fly-a sh particles. Possible modes of formation which include vapor depositi on, accumulation and annealing of fume particles, or recrystallization of iron sulfide droplets were investigated.