Low-temperature treatment of polyethylene plastics and semi-coke mixture and CO2 gasification of finely ground products

A new treatment process for waste plastics is proposed, in which mixtures of waste plastics and solid carbon material are heated under an inert atmosphere at low temperatures. Two variables-temperature and plastics addition ratio-were considered during the heat treatment and crushing tests. A series of tests was performed to explore the corresponding mechanism. The optimum heat treatment temperature was 723 K, and the optimum plastic addition ratio was 20%. Additionally, non-isothermal CO2 gasification tests of ground products conducted using a thermogravimetric analyser revealed that the gasification reactivity of products with plastic addition was better than that of the coal powder. The reactivity of the samples was in the following order: 20% > 25% > 15% > 10% > semi-coke. Three representative kinetics models, random pore model (RPM), volume reaction model (VM), and unreacted core model (URCM), were employed to analyse the kinetics of gasification. The RPM and VM were found to be suitable for the gasification of the products, which were characterised by various methods, and the heat treatment mechanism was analysed and discussed from the physical and chemical aspects. The findings herein are expected to be useful for the treatment of waste plastics.