Transformation of sulfur in coal during rapid pyrolysis at high temperatures

The Guizhou high-sulfur coal and its demineralized coal were rapidly pyrolyzed in a drop tube furnace under an argon atmosphere at the high temperatures ranging from 700°C to 1200°C. The effects of temperature and minerals on the transformations between various forms of sulfur, including sulphidic sulfur and thiophenic sulfur, were studied using X-ray photoelectron spectroscopy (XPS) during rapid pyrolysis. The total sulfur content was determined by the infrared-red sulfur analyzer (ISA) and confirmed by XPS analysis. The total sulfur retention in chars did not simply decrease with increasing temperature but increased at a specific temperature in both raw coal and demineralized coal. Thiophenic sulfur was the primary sulfur compound found on the char surface during rapid pyrolysis at different temperatures. Sulfur in different forms decomposed and transformed at high temperatures and this was evidenced by the complete decomposition of sulphidic sulfur at 1000°C and the increase of thiophenic sulfur content at 1100°C. These results indicate that other forms of sulfur could transform into thiophenic sulfur.