Thermodynamics and Reduction of Bi2O3 in Waste Tire-Derived Atmosphere

Abstract

The present study aimed to investigate reduction behavior of Bi2O3 in the gaseous atmosphere generated by the pyrolysis of waste tires. Thermodynamic analysis carried out in the Bi-O-C-H-S-Ar system predicted that Bi2O3 could be reduced to Bi in the temperature range 700-900 K. Bi2O3 reduction experiments were carried out as a function of reactant mass ratio (m(tire)/m(Bi2O3) = 0-10) and temperature (600-900 K). The extent of tire pyrolysis increased as the temperature was raised to 900 K. The degree of Bi2O3 reduction increased with increasing tire pyrolysis, while the waste pyrolysis process controlled Bi2O3 reduction. The oxide reduction was incomplete, when only waste tires were used. Adding a minor amount of waste high-density polyethylene to the tires sufficed for full Bi2O3 reduction at 900 K. The reduction reactions and a model for the morphological evolution are presented. Large Bi shots formed owing to the coalescence of the liquid Bi droplets at the reduction temperature.