Design of plastic waste chemical recycling process considering uncertainty

Abstract

The selection of mixed plastic waste recycling technologies directly influences product distribution and thus the overall process economics. This study presents an integrated chemical recycling process that combines pyrolysis, hydrogenolysis, and hydrocracking to transform plastic waste directly into high-value fuel products, eliminating the need for further upgrading. A mixed-integer nonlinear programming model is formulated to consider the selection of reaction pathways considering fuel properties to ensure compliance with product specifications. Robust optimization is used to incorporate the effect of fuel property and economic uncertainty on the process design. Under nominal conditions, the optimized chemical recycling process demonstrates strong economic performance with a unit net present value of $366/t plastic waste. Different levels of conservatism are considered to account for uncertainty. The optimized process shows a robust performance by leveraging different combinations of depolymerization technologies and adjusting the product portfolio.