Co-pyrolysis of waste plastics and tires: Influence of interaction on product oil and gas composition

Abstract

The co-pyrolysis of different waste plastics and tires was carried out to investigate the effect of their interaction during co-pyrolysis on the yield and composition of the product oils and gases. Different types of waste plastics, consisting of high density polyethylene (HDPE), low density polyethylene (LDPE), polypropylene (PP), polystyrene (PS), and polyethylene terephthalate (PET), were co-pyrolysed with the waste tires using a fixed bed batch pyrolysis reactor. The main gases produced from the individual plastics and tires were hydrogen, methane, ethane, ethene, propane, propene, butane, and butene, whereas PET produced mainly carbon dioxide and carbon monoxide. GC/MS analysis of the product oil produced from tire pyrolysis were mostly aromatic compounds produced from the rubber components of the tire. For HDPE, LDPE and PP pyrolysis, the oil produced was of mainly aliphatic composition, PS pyrolysis gave a considerable portion of single ring aromatic and polycyclic aromatic compounds and PET formed mainly oxygenated compounds and aromatic compounds. Co-pyrolysis of the plastics and tires resulted in an increase in gas yield above what would be expected from feedstock addition, suggesting interaction between the feedstocks. Also, oil analysis of the co-pyrolysis oils indicated significant shifts in the oil composition. For the mixed tire with HDPE and LDPE, aliphatic compounds were increased above that expected from addition with lower yields of single ring and polycyclic aromatic hydrocarbons. In contrast, mixing tire with PP produced higher yields of aromatic hydrocarbons and lower yield of aliphatic and alicyclic compounds than expected from additive calculation. Mixing tire with PS produced higher than expected single ring aromatic compounds but lower yields of polycyclic aromatic and alicyclic hydrocarbons. For the tire-PET co-pyrolysis, the production of oxygenated compounds was decreased in comparison to the expected additive data.