A review of resource recovery from waste plastics via pyrolysis and gasification
Jigang Zhang, Zhiyuan Chu, Ruolan Cao, Xuebin Wu, Kuihua Han
Abstract
The global accumulation of waste plastics leads to environmental problems and waste of resources. Physical and chemical methods are used to treat waste plastics. Among them, pyrolysis and gasification show the advantages of efficient treatment and high resource recovery, which are recognized as promising methods for the production of pyrolysis hydrocarbons and H 2 . This review summarized the sources and types of waste plastics, and the current situation of pyrolysis and gasification of waste plastics. The mechanisms during the pyrolysis and gasification, influencing factors, product characteristics, reactor types for pyrolysis and gasification were discussed. The application of suitable catalysts should be considered in pyrolysis and gasification. The treatment of waste plastics via pyrolysis and gasification is still a long way from industrial application. Over 90 wt% of the oil or 25 wt% of the H 2 can be recovered through pyrolysis and gasification. In addition, H 2 production from carbon-based fuel gasification enhanced by CO 2 capture from calcium-based materials was reviewed, and a pyrolysis/gasification of waste plastics process for H 2 production using the Ni-Fe/CaO-based catalyst was proposed. In the pyrolysis stage, Ni and Fe act as active metals to promote the decomposition of plastic molecules. CaO is used as a dechlorinating agent to reduce HCl production in the pyrolysis of chlorinated plastics. In the gasification stage, the removal of carbon accumulation from pyrolysis in Ni-Fe/CaO-based catalysts is enhanced due to CO 2 capture by CaO. Finally, the problems in the pyrolysis/gasification of waste plastics were summarized and the development prospects were outlined.