Production of CO-rich syngas through CO2-Mediated pyrolysis of plastic waste and its practical use for power generation

Abstract

Pyrolysis of plastic waste has emerged as a strategic measure to produce liquid fuel, expanding applicability in internal combustion engines under controllable equivalence ratio. However, a difficulty in the precise control of hydrocarbon (HC) chain lengths in the liquid fuel still restricts its reliable utilization. To produce more combustible fuel, transforming plastic waste into gaseous fuels may be more viable approach. This study thus investigated a pyrolytic conversion of plastic waste, plastic bag waste (PBW), into syngas while leveraging carbon dioxide (CO₂) as a partial oxidative agent. Pyrolysis of PBW generates a broad spectrum of HCs, which are unsuitable as transportation fuel. However, introducing CO₂ enabled its interaction with PBW-derived pyrogenic HCs, partially shortening their carbon chain lengths. A nickel (Ni) catalyst was introduced to accelerate the reaction kinetics to govern the functional reactivity of CO₂. Peak intensities of pyrogenic HCs were notably reduced, with effective conversion into CO-rich syngas, contributing to the enhanced carbon availability and suppressed CO₂ emission within the proposed pyrolysis system. Catalytic pyrolysis was conducted under diverse temperatures (500, 600, and 700 °C) and CO₂ concentrations (0, 20, 50, and 80 vol% CO₂) to optimize the mechanistic reactivity of CO₂. For a practical evaluation, the resulting CO-rich syngas was simulated in a gas turbine cycle model for power generation. The thermodynamic variables were determined using the syngas compositional matrix and then used to estimate gas turbine performances including work output and thermal efficiency. The thermal efficiency of the gas turbine cycle was significantly enhanced when utilizing CO-rich syngas produced from CO₂-mediated catalytic pyrolysis, demonstrating more than two-fold increase compared with commercial natural gas.