Low rank coal for fuel production via microwave-assisted pyrolysis: A review

Not only its abundant resources, but also low rank coal (LRC) can be transformed into different valuable chemical products via syngas. This review focuses on technology of microwave-assisted pyrolysis (MAP) applied on LRC as a promising technique of thermochemical conversion that can transform LRC into high quality syngas. A confined number of reviews has been selected and evaluated to observe current status and challenges of the technology, including essential production factors, pretreatment of LRC, and heating characteristics of MAP. Experimental research on catalytic and non-catalytic of the technology focusing on the product distribution resulting from conventional pyrolysis (CP) are also discussed. The best yields of char, tar, and syngas from CP at 900 °C were 2%, 41%, and 58%, respectively. Meanwhile, the best yields of char, oil and syngas from MAP at 620 °C were 32%, 15% and 53%, respectively. Finally, this review evaluates the advantages and challenges of the technology and the milestones to be achieved in near future.