Entrained-Flow Gasification for the Utilization of Pyrolysis Oil from Mixed Plastic Waste

Abstract

Plastic pyrolysis aims to process plastic waste into petrochemical feedstocks by addressing waste fractions that are unsuitable for mechanical recycling due to their complex composition. Steam cracking of the resulting pyrolysis oils requires low levels of contaminants, limiting the acceptable contaminant level in feedstocks for chemical recycling. The utilization of pyrolysis oil in entrained-flow gasification (EFG) can overcome this limitation, as EFG is designed to process low-quality feedstocks such as heavy fuel oil (HFO) with high heteroatom content. For process assessment, we developed a flowsheet model for EFG of pyrolysis oil from automotive plastic waste (APW) and carried out a comprehensive life cycle assessment (LCA). HFO and APW pyrolysis oil as feedstocks for EFG show minimal differences regarding process efficiencies. In combination with the pyrolysis step, overall carbon efficiencies of 41% (methanol syngas) and 62% (Oxo syngas) are reached. Despite differing carbon efficiencies, both waste-to-syngas routes show nearly identical net climate change impacts (CCI) of 0.14 kg of CO2e/kg of APW, indicating that the choice of syngas product composition does not significantly influence the CCI. In comparison, the established current practice of incineration with energy recovery (waste-to-energy) causes a CCI that is 1 kg of CO2e/kg of APW higher.