Remediation of plastic waste generated during the COVID-19 pandemic: A conceptual process design of pyrolysis using polyethylene, polypropylene, polystyrene based polymers

Abstract

During the COVID-19 pandemic, the increase in plastic-based personal protective equipment has raised concerns about managing medical waste and protecting the environment. This study highlights the need for effective waste management strategies by creating a conceptual process flow diagram and investigating thermal treatment methods like pyrolysis as potential solutions. Using computational modeling and process optimization, the study examines different polymer blends, including High-Density Polyethylene (HDPE), Polystyrene (PS), and Polypropylene (PP), to understand how they behave during pyrolysis and the yields they produce. Two pyrolysis schemes have been developed to handle various polymer blends. In Scheme 1, the liquefied polymer is preheated and then pyrolyzed in a reactor, producing a vapor stream and a residue stream (carbon). The vapor stream is cooled to enhance liquid oil production and then is separated in a distillation column to isolate liquid oil from pyrogas. Scheme 2 follows a similar process but converts a significant portion of liquid hydrocarbons to gas in the distillation column, requiring further gas processing in a one-stage separator column. The results show that temperature significantly impacts liquid yield, with specific temperature ranges leading to increased yield. Additionally, the composition of the polymers and the rate at which the material is fed into the process affect the yields, with specific blends showing promise for higher liquid yield. This study emphasizes the importance of accurate process modeling to optimize the operational parameters and improve the economic viability of plastic pyrolysis technology presenting a promising opportunity to convert plastic waste into valuable resources.