Migration and transformation of sulfur during pyrolysis of waste tires for high-value utilization of poly-generation products

Abstract

The three-state pyrolysis products of waste tires pyrolysis have high utilization value, and the migration and transformation of sulfur during pyrolysis of waste tires is one of the most important factors affecting product properties. Understanding the mechanism of sulfur migration and conversion during waste tire pyrolysis is necessary for high value utilization of poly-generation products. This work focused on the effects of different factors on product distribution and sulfur transformation during waste tires pyrolysis. The results showed that the migration of sulfur was predominantly attributable to the decomposition, conversion, and migration of aliphatic and thiophene sulfur to pyrolysis oil and gases. The decomposition rate of aliphatic sulfur and thiophene sulfur exhibits a gradual increase with the increase of pyrolysis temperatures and heating rates. However, the decomposition rate of aliphatic sulfur and thiophene sulfur in the recovered carbon black (rCB) exhibited a decline as the particle size of waste tires increased, with retention rates increasing from 12.4% to 16.6% for aliphatic sulfur and from 29.6% to 39.8% for thiophene sulfur. A large number of intermediate products ·SH and ·S radicals were produced, and this process was verified using DFT (Density Functional Theory) calculations. This paper provided a partial knowledge of sulfur migration and transformation in the three-state pyrolysis products during waste tires pyrolysis, which can provide valuable information for high-value utilization of waste tires and control technologies of pollutants emission.

Keywords: Pyrolysis; Sulfur; Sulfur distribution; Sulfur transformation; Waste tires.