Process design for plastic waste pyrolysis: Yield analysis and economic assessment

The widespread use of plastic products and inadequate waste management systems have rendered plastic waste a major source of environmental pollution, thereby necessitating effective plastic recycling methods. In this study, we propose two pyrolysis processes for recycling plastic waste using Aspen Plus: a base process and an alternative process. The main difference lies in the condensation and separation methods used to produce pyrolysis oil. In the base process, condensation is carried out using a cooler, followed by decomposition with a flash drum. In contrast, the alternative process utilizes a distillation column for both condensation and separation. The results showed that PS achieved the highest oil yield of 81.3 %, while PS/PE exhibited the greatest improvement, with a 27.34 % increase in oil production yield in the alternative process compared to the base process. However, the alternative process incurs higher operating and capital costs due to the precise control requirements, particularly for feedstocks like PS/PE/PP/PET, which had the highest energy production cost at 31.07×10 ⁻⁴ $/ MJ compared to 27.85×10 ⁻⁴ $/ MJ in the base process. Despite these higher costs, the alternative process significantly improved oil production, especially for plastics such as PS and PS/PE. These findings underscore the importance of selecting pyrolysis processes based on feedstock composition and specific recycling goals, highlighting the trade-off between higher yields and increased energy production costs and emphasizing the need for balance.