Parametric investigation of the effects on waste tire pyrolysis oil in a downdraft tube reactor

The operating parameters in fast pyrolysis waste tires play a paramount role on the yield and selectivity of pyrolytic products. To figure out the detailed influence on the yield of tire pyrolysis oil (TPO) and selectivity of D-limonene and monoaromatics (BTXs), the operating parameters on laboratory-scale downdraft tube reactor, i.e., pyrolysis temperature, particle size, and carrier gas flow rate, were investigated during waste tires pyrolysis. The thermal decomposition of the waste tire was performed on the thermogravimetric analyzer using a high heating rate at 700 °C min−1 first, which suggested the predominant decomposition occurred between 350 and 600 °C. Results obtained from the downdraft tube reactor and principal component analysis showed that temperature and carrier gas flow rate were the key factors that affected the yield and composition of TPO, whereas the effects of particle size were limited. The yield of TPO reached a maximum value of 41.90 wt% under optimal conditions (500 °C, 0.30–0.45 mm, and 150 mL min−1). Correspondingly, the selectivity of D-Limonene and BTXs in TPO was 18.55 wt% and 24.08 wt% by the correlation of the external standard method, respectively. Furthermore, the plausible formation mechanism of D-Limonene and the further conversion pathways affected by experimental conditions were also suggested.