The behavior of organic sulfur species in fuel during chemical looping gasification.

Uncoupling chemical looping gasification (CLG), the organic sulfur evolution was simulated and explored qualitatively and quantitatively using typical sulfur compounds on TG-MS and temperature-programmed fixed bed. The HS radical in the reductive atmosphere easier converted to HS and COS. HO activated the evolution of S which was stably bonded to carbon, and H generated from gasification and oxidation of reductive Fe by HO contributed to the release of sulfur. The proportion of HS released from sulfur compounds was greater than 87% in steam gasification, and more than 60% during CLG. Oxygen carriers promoted the conversion of sulfur to SO in the mid-temperature region (500 °C-700 °C), and HS in the high temperature region (700 °C-900 °C). Sulfur species played a pivotal role in sulfur evolution at low temperature of CLG. The organic sulfur in mercaptan and benzyl were more easily converted and escaped than in thiophene and phenyl. The thermal stability of sulfur species, the presence of steam and OC affected the initial temperature and peak concentration of gas sulfur release as well as sulfur distribution. Consequently, CLG strengthened the sulfur evolution, and made it possible to targeted restructure the distribution of sulfur by regulating process parameters, or blending fuel with different sulfur species for emission reduction, and selective conversion of sulfur.