Sulfur transformation behaviors and synergistic mechanism during co-pyrolysis of coal and waste tire

Sulfur migration plays a crucial role in determining pollutant emissions, products quality and process sustainability during co-pyrolysis of coal and waste tire. However, the sulfur transformation pathways during co-pyrolysis of coal and waste tire remain unclear. In this work, the sulfur migration behaviors and transformation mechanism during co-pyrolysis of Yulin coal (YL) and waste tire (WT) were systematically elucidated by comprehensively evaluating the effects of heating rate, temperature and blending ratio on sulfur distribution in char, liquid and gaseous products on an infrared-heated fixed-bed reactor. Results showed that sulfur from YL pyrolysis was mainly distributed in liquid and char products, whereas sulfur from WT was predominantly retained in char. During co-pyrolysis, sulfur transfer from char to liquid products was promoted and sulfur release into gaseous phase was suppressed. Positive synergistic effects were mainly observed for sulfur distribution in liquid products, whereas negative synergistic effects dominated gaseous sulfur evolution. Among the S -containing gases, H 2 S formation was obviously inhibited at 550 – 600 °C. XRD and XPS analyses revealed that co-pyrolysis promoted the conversion of organic sulfur species into inorganic sulfides. Meanwhile, WT-derived ZnO participated in sulfur stabilization through the formation of ZnS species. These findings elucidate the coupled radical-mediated sulfur redistribution and Zn -assisted sulfur immobilization mechanism during coal/waste tire co-pyrolysis, providing insights into sulfur transformation and emission control during co-pyrolysis process.