XAS combined with Py-GC study on the effects of temperatures and atmospheres on sulfur release and its transformation behavior during coal pyrolysis

Abstract

YanZhou (YZ) coal with comparably high organic sulfur and high pyrite content was selected to investigate the effects of temperatures on sulfur release and its transformation during pyrolysis under Ar and CO2 atmospheres. Pyrolysis connected with gas chromatography (Py-GC) was used to analyze the sulfur containing gases of H2S, COS and SO2, and the sulfur transformation during pyrolysis was measured by Sulfur K-edge X-ray absorption spectroscopy (S-XAS). For YZ raw, deashed and depyrited coals, desulfurization ratios gradually increase with the increasing temperatures, while their char yields gradually decrease under both atmospheres. Under Ar atmosphere, minerals in YZ coal have catalytic effect on the decomposition of sulfurs. However, the effect of minerals on sulfur decomposition is different under CO2 atmosphere. Under CO2 atmosphere, the release amounts of H2S, COS and SO2 for each sample are higher than that under the Ar atmosphere and the difference becomes more significant after 600 °C. This suggests that CO2 atmosphere is more helpful for the decomposition of stable sulfur at comparatively higher temperatures. Based on the analysis of Sulfur K-edge XAS, CO2 atmosphere can promote the decomposition of stable FeS and thiophenes during pyrolysis. Thus, based on the analysis of Py-GC and Sulfur K-edge XAS, CO2 atmosphere is more beneficial for the release of sulfur containing gases and for the decomposition of stable sulfur than Ar atmosphere. This provides detailed information about the effects of temperatures on sulfur release and transformation behavior during pyrolysis under CO2 atmosphere.