A novel method for industrial production of clean hydrogen (H2) from mixed plastic waste

• Published in: International journal of hydrogen energy 2023-05, Vol.48 (40), p.15037-15052
• Main Authors: Ganza, Patient E., Lee, BongJu
• Format: Article
• Language: English
• Subjects: Contaminant; Electric furnace; Hybrid microwave plasma enhanced gasification (HMPEG); Microwave heating; Plastic waste; Rotary pyrolyzer
• ISSN: 0360-3199; 1879-3487
• DOI: 10.1016/j.ijhydene.2023.01.010

This study describes a novel Hybrid Microwave Plasma Enhanced Gasification (HMPEG) method for converting plastic waste into hydrogen (H2). Thermal processing of plastic waste is a low-cost method of producing H2. Current methods, however, such as pyrolysis and gasification, are limited by inefficient heating and contaminants in syngas, resulting in a low H2 yield. Our approach consists of a novel rotary pyrolysis reactor that employs an external microwave heater and an electrodeless microwave torch reformer, thereby addressing issues with current methods. In this study, pyrolysis of mixed plastic produces pyro-gas which is reformed at a temperature above 1500 °C by the steam plasma torch powered by microwave. The result is a 150 g/kg H2 yield with a 67 vol.% higher production rate, an H2/CO ratio of 7, and a conversion efficiency of 97.4%. Tar and dioxin concentrations in the syngas were found to be 0.078 g/Nm3 and 0.024 ng-TEQ/Nm3, respectively, much less than the legal limit. A novel microwave pyrolyzer cuts electrical power consumption by half, and the pure H2 produced is suitable for direct use in hydrogen cars, power generation, and other applications. Once implemented, the energy-efficient HMPEG could aid in expanding H2 commercial plants that use plastic waste as a raw input fuel. [Display omitted] •The efficiency of producing H2 stands at 67% and syngas reforming efficiency is 65.8%.•Hybrid process minimizes bio-oils by converting the maximum tar content in pyro-gas.•The plasma torch allows the complete removal of dioxin and other toxic byproducts.•We propose a novel rotary microwave-heated pyrolyzer with impressive energy saving.