[Investigation of inorganic sulfur decomposition in a coal-like environment during pyrolysis]

An activated charcoal (AC) was used to simulate coal-like environment, and the inorganic sulfur (pyrite or ferrous sulfate) was mixed with it in some ways. The dynamic characteristics and structure changes of FeS2 and FeSO4 with and without AC during pyrolysis, were investigated by temperature-programmed decomposition-flame photometric detector or mass spectrometer (TPD-FPD/ MS) and extended X-ray absorption fine Structure (EXAFS) spectroscopy. It is found that the decomposition of FeSO4 impregnated onto AC mainly happened between 200 degrees C and 500 degrees C , while the pure FeSO4 decomposed at around 450 degrees C - 600 degrees C. The comparison shows that the existence of AC lowered the decomposition temperature of FeSO4, and made the emission of sulfur more complex as well. However, the decomposition temperature of pyrite wasn't varied by the physical mixing with AC. Furthermore, the decomposition degree of pyrite depended on the existence of AC and the pyrolysis atmosphere used. Above 400 degrees C, the evolution of sulfur became remarkable. At around 550 degrees C the sulfur in the second sphere of Fe-S-S was lost, and the pyrolysis product FeS appeared simultaneously.