Production of aviation fuel via thermal cracking of plastic waste

Abstract

Despite the calorific value of plastic waste being comparable to that of fossil fuels, its direct utilisation in the internal combustion engine is not a viable option due to a technical difficulty in optimising the equivalence ratio. To address this issue, this study proposes a pyrolysis system for the conversion of plastic waste, especially high density polyethylene (HDPE), into liquid fuels compatible with aircraft turbojet engines. Given a broad spectrum of pyrogenic hydrocarbons (HCs) derived from HDPE, it is important to shorten the chain length to produce aviation fuel-like products with carbon numbers ranging from 8 to 16. To this end, this study modified the typical pyrolysis setup by additionally adopting a heating element, isothermally operated at 500–800 °C. Also, the condensation system for collecting the pyrogenic HCs was designed using two consecutive units (set as 20 and −40 °C) for the selective recovery of jet-fuel-range HCs. The reaction temperature of 600 °C exhibited the similar composition of HDPE-derived fuel with commercial aviation fuels (Jet-A, JP-8, and JP-5). Subsequently, thermodynamic calculations of HCs collected in the second trap were performed in an ideal turbojet engine cycle. It was confirmed that the fuel performances of HDPE-derived fuel (produced at 600 °C) were comparable to commercial ones. Therefore, this study proposed that modification of pyrolysis and condensation system facilitated the production of jet-fuel-range HCs derived from HDPE.