Unveiling the migration and transformation pathways of sulfur during combustion and pyrolysis of waste textiles

Abstract

Converting of waste textiles (WT) into fuel is considered one of the feasible pathways to promote the circular economy of textile industry, at which the sulfur problem is unknown. In this study, we tried to unveil the sulfur problem during the combustion/pyrolysis process of WT, including wool hair (WH), camel hair (CH) and rabbit hair (RH) by thermogravimetry-mass spectrum simulation and batch experiments. Results showed that CH and WH showed the best combustion and pyrolysis possibility, based on their TG-DTG curves and thermal characteristic parameters. The sulfur-containing gas mainly emitted as H₂S and SO₂ during WT combustion and pyrolysis, therein, combustion was conducive to the release of sulfur. Regardless of combustion or pyrolysis, standardized SO₂ outputs lied at nonnegligible level (62.33––64.67 kg/t from combustion and 51.02––54.28 kg/t from pyrolysis). Correspondingly, only 4 % of sulfur was trapped in WT combustion ash as sulfate form, while approximately 23 % sulfur was trapped in pyrolytic char and tar phases as organic sulfur forms (e.g. thiophene, ether, acid and ester). This study unveils a neglected sulfur during combustion and pyrolysis of waste textiles.