Utilization of carbon dioxide (CO2) in thermochemical treatment of waste plastics may significantly help to improve CO2 recycling, thus simultaneously curtailing dioxins/furans and CO2 emissions. Although CO2 is not such an effective gasifying agent as steam, a few investigations have explored the utilization of CO2 in conjunction with steam to achieve somewhat higher carbon conversion. This work presents a comparative evaluation study of CO2 and steam gasification of a typical post-consumer waste plastics mixture using an Aspen Plus equilibrium model. The effect of flow rate of gasifying medium (CO2 and/or steam) and gasification temperature on product gas composition, carbon conversion, and cold gas efficiency has been analyzed. Simulation results demonstrate that CO2 can serve as a potential gasifying agent for waste plastics gasification. The resulting product gas was rich in CO whereas CO2-steam blends yield a wider H2/CO ratio, thus extending the applications of the product gas.
Keywords: Waste plastics; carbon dioxide utilization; energy recovery; equilibrium modeling; gasification.